A078585 -id:A078585 - cp's OEIS frontend

A001620 Decimal expansion of Euler's constant (or the Euler-Mascheroni constant), gamma.

5, 7, 7, 2, 1, 5, 6, 6, 4, 9, 0, 1, 5, 3, 2, 8, 6, 0, 6, 0, 6, 5, 1, 2, 0, 9, 0, 0, 8, 2, 4, 0, 2, 4, 3, 1, 0, 4, 2, 1, 5, 9, 3, 3, 5, 9, 3, 9, 9, 2, 3, 5, 9, 8, 8, 0, 5, 7, 6, 7, 2, 3, 4, 8, 8, 4, 8, 6, 7, 7, 2, 6, 7, 7, 7, 6, 6, 4, 6, 7, 0, 9, 3, 6, 9, 4, 7, 0, 6, 3, 2, 9, 1, 7, 4, 6, 7, 4, 9

Offset: 0

N. J. A. Sloane

Yee (2010) computed 29844489545 decimal digits of gamma.
Decimal expansion of 0th Stieltjes constant. - Paul Muljadi, Aug 24 2010
The value of Euler's constant is close to (18/Pi^2)*Sum_{n>=0} 1/4^(2^n) = 0.5770836328... = (6/5) * A082020 * A078585. - Arkadiusz Wesolowski, Mar 27 2012

			0.577215664901532860606512090082402431042...

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 3.
John H. Conway and Richard K. Guy, The Book of Numbers, New York: Springer-Verlag, 1996. See pp. 24, 259-262.
S. R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, pp. 28-40, 166, 365.
C. F. Gauss, Disquisitiones Arithmeticae, Yale, 1965; see p. 359.
B. Gugger, Problèmes corrigés de Mathématiques posés aux concours des Ecoles Militaires, Ecole de l'Air, 1992, option MP, 1ère épreuve, Ellipses, 1993, pp. 167-184.
Jan Gullberg, Mathematics from the Birth of Numbers, W. W. Norton & Co., NY & London, 1997, §8.3 Infinite Series, pp. 273-274.
J. Havil, Gamma: Exploring Euler's Constant, Princeton Univ. Press, 2003.
J.-M. Monier, Analyse, Exercices corrigés, 2ème année, MP, Dunod, Exercice 4.3.14, pages 371 and 387, 1997.
Paulo Ribenboim, The Little Book of Bigger Primes, Springer-Verlag NY 2004. See p. 166.
Joel L. Schiff, The Laplace Transform: Theory and Applications, Springer-Verlag New York, Inc. (1999). See p. 44.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
Jerome Spanier and Keith B. Oldham, "Atlas of Functions", Hemisphere Publishing Corp., 1987, chapter 1, equation 1:7:5 at page 13.
David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987, p. 28.
E. T. Whittaker and G. N. Watson, A Course of Modern Analysis, Cambridge Univ. Press, 4th ed., 1990.

Harry J. Smith, Table of n, a(n) for n = 0..20000
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
Iaroslav V. Blagouchine, Expansions of generalized Euler's constants into the series of polynomials in 1/Pi^2 and into the formal enveloping series with rational coefficients only, arXiv:1501.00740 [math.NT], 2015-2016; Journal of Number Theory (Elsevier), Volume 158, pages 365-396, 2016.
D. Bradley, Ramanujan's formula for the logarithmic derivative of the Gamma function, arXiv:math/0505125 [math.CA], 2005.
R. P. Brent, Ramanujan and Euler's constant.
R. P. Brent and F. Johansson, A bound for the error term in the Brent-McMillan algorithm, arXiv 1312.0039 [math.NA], Nov. 2013.
C. K. Caldwell, The Prime Glossary, Euler's constant.
D. Castellanos, The ubiquitous pi, Math. Mag., 61 (1988), 67-98 and 148-163.
Chao-Ping Chen, Sharp inequalities and asymptotic series of a product related to the Euler-Mascheroni constant, Journal of Number Theory, Volume 165, August 2016, Pages 314-323.
E. Chlebus, A recursive scheme for improving the original rate of convergence to the Euler-Mascheroni constant, Amer. Math. Mnthly, 118 (2011), 268-274.
M. Coffey and Jonathan Sondow, Rebuttal of Kowalenko's paper as concerns the irrationality of Euler's constant, arXiv:1202.3093 [math.NT], 2012; Acta Appl. Math., 121 (2012), 1-3.
Dave's Math Tables, Gamma Constant.
Philippe Deléham, Letter to N. J. A. Sloane, Apr 14 1997.
Thomas and Joseph Dence, A survey of Euler's constant, Math. Mag., 82 (2009), 255-265.
Pierre Dusart, Explicit estimates of some functions over primes, The Ramanujan Journal, 2016.
Ph. Flajolet and I. Vardi, Zeta function expansions of some classical constants.
X. Gourdon and P. Sebah, The Euler constant gamma.
Kalpok Guha and Sourangshu Ghosh, Measuring Abundance with Abundancy Index, (2021).
Brady Haran and Tony Padilla, The mystery of 0.577, Numberphile video, 2016.
J. C. Kluyver, Euler's constant and natural numbers, Proc. K. Ned. Akad. Wet., 27(1-2) (1924), 142-144.
D. E. Knuth, Euler's constant to 1271 places, Math. Comp. 16 1962 275-281.
Stefan Krämer, Euler's Constant γ=0.577... Its Mathematics and History.
Richard Kreckel, 116 million digits of Euler's constant (bzipped).
A. Krowne, PlanetMath.org, Euler's constant.
Jeffrey C. Lagarias, Euler's constant: Euler's work and modern developments, arXiv:1303.1856 [math.NT], 2013; Bull. Amer. Math. Soc., 50 (2013), 527-628.
M. Lerch, Expressions nouvelles de la constante d'Euler, S.-B. Kgl. Bohmischen Ges. Wiss., Article XLII (1897), Prague (5 pages).
Eric Naslund, Euler-Mascheroni constant expression, further simplification, MathStackExchange.
T. Papanikolaou, Plouffe's Inverter, Euler's constant to 1000000 decimals.
Michael Penn, Euler's other constant, YouTube video (2023).
S. Plouffe, using data from J. Borwein, 170000 digits of Euler or gamma constant [archived copy of a page on WorldWideSchool.org which doesn't exist any mode, cf. "Euler" link in left column].
S. Ramanujan, A series for Euler's constant, Messenger of Math., 46 (1917), 73-80.
S. Ramanujan, Question 327, J. Ind. Math. Soc.
Jonathan Sondow, An antisymmetric formula for Euler's constant, Math. Mag. 71 (1998), 219-220.
Jonathan Sondow, Criteria for irrationality of Euler's constant, Proc. Amer. Math. Soc. 131 (2003), 3335-3344.
Jonathan Sondow, Double integrals for Euler's constant and ln(4/Pi) and an analog of Hadjicostas's formula, arXiv:math/0211148 [math.CA], 2002-2004; Amer. Math. Monthly 112 (2005), 61-65.
Jonathan Sondow, An infinite product for e^gamma via hypergeometric formulas for Euler's constant, gamma, arXiv:math/0306008 [math.CA], 2003.
Jonathan Sondow, A hypergeometric approach, via linear forms involving logarithms, to irrationality criteria for Euler's constant. With an Appendix by Sergey Zlobin, arXiv:math/0211075 [math.NT], 2002-2009; Math. Slovaca 59 (2009), 1-8.
Jonathan Sondow, New Vacca-Type Rational Series for Euler's Constant and Its "Alternating" Analog ln(4/Pi), arXiv:math/0508042 [math.NT], 2005; Additive Number Theory, Festschrift In Honor of the Sixtieth Birthday of Melvyn B. Nathanson (D. Chudnovsky and G. Chudnovsky, eds.), Springer, 2010, pp. 331-340.
Jonathan Sondow and Petros Hadjicostas, The generalized-Euler-constant function gamma(z) and a generalization of Somos's quadratic recurrence constant, arXiv:math/0610499 [math.CA], 2006; J. Math. Anal. Appl. 332 (1) (2007), 292-314.
Jonathan Sondow and S. Zlobin, Integrals over polytopes, multiple zeta values and polylogarithms, and Euler's constant, arXiv:0705.0732 [math.NT], 2007; Math. Notes, 84 (2008), 568-583, Erratum p. 887.
Jonathan Sondow and W. Zudilin, Euler's constant, q-logarithms and formulas of Ramanujan and Gosper, arXiv:math/0304021 [math.NT], 2003; Ramanujan J. 12 (2006), 225-244.
D. W. Sweeney, On the computation of Euler's constant, Math. Comp., 17 (1963), 170-178.
Eric Weisstein's World of Mathematics, Euler-Mascheroni Constant.
Wikipedia, Stieltjes constants.
A. Y. Yee, Large computations.
Index entries for sequences related to Beatty sequences.

Cf. A002852 (continued fraction).
Cf. A073004 (exp(gamma)) and A094640 ("alternating Euler constant").
Cf. A231095 (power tower using this constant).
Cf. A199332, A252898.
Denote the generalized Euler constants, also called Stieltjes constants, by Sti(n).
Sti(0) = A001620 (Euler's constant gamma) (cf. A262235/A075266),
Sti(1/2) = A301816, Sti(1) = A082633 (cf. A262382/A262383), Sti(3/2) = A301817,
Sti(2) = A086279 (cf. A262384/A262385), Sti(3) = A086280 (cf. A262386/A262387),
Sti(4) = A086281, Sti(5) = A086282, Sti(6) = A183141, Sti(7) = A183167,
Sti(8) = A183206, Sti(9) = A184853, Sti(10) = A184854.

EulerGamma(250); // G. C. Greubel, Aug 21 2018

Maple
```
Digits := 100; evalf(gamma);
```

RealDigits[ EulerGamma, 10, 105][[1]] (* Robert G. Wilson v, Nov 01 2004 *)
(1/2) N[Sum[PolyGamma[0, 1/2 + 2^k] - PolyGamma[0, 2^k], {k, 0, Infinity }], 30] (* Dimitri Papadopoulos, Nov 30 2016 *)

default(realprecision, 20080); x=Euler; d=0; for (n=0, 20000, x=(x-d)*10; d=floor(x); write("b001620.txt", n, " ", d));  \\ Harry J. Smith, Apr 15 2009

from sympy import S
def aupton(digs): return [int(d) for d in str(S.EulerGamma.n(digs+2))[2:-2]]
print(aupton(99)) # Michael S. Branicky, Nov 22 2021

Limit_{n->oo} (1 + 1/2 + ... + 1/n - log(n)) (definition).
Sum_{n>=1} (1/n - log(1 + 1/n)), since log(1 + 1/1) + ... + log(1 + 1/n) telescopes to log(n+1) and lim_{n->infinity} (log(n+1) - log(n)) = 0.
Integral_{x=0..1} -log(log(1/x)). - Robert G. Wilson v, Jan 04 2006
Integral_{x=0..1,y=0..1} (x-1)/((1-x*y)*log(x*y)). - (see Sondow 2005)
Integral_{x=0..oo} -log(x)*exp(-x). - Jean-François Alcover, Mar 22 2013
Integral_{x=0..1} (1 - exp(-x) - exp(-1/x))/x. - Jean-François Alcover, Apr 11 2013
Equals the lim_{n->oo} fractional part of zeta(1+1/n). The corresponding fractional part for x->1 from below, using n-1/n, is -(1-a(n)). The fractional part found in this way for the first derivative of Zeta as x->1 is A252898. - Richard R. Forberg, Dec 24 2014
Limit_{x->1} (Zeta(x)-1/(x-1)) from Whittaker and Watson. 1990. - Richard R. Forberg, Dec 30 2014
exp(gamma) = lim_{i->oo} exp(H(i)) - exp(H(i-1)), where H(i) = i-th Harmonic number. For a given n this converges faster than the standard definition, and two above, after taking the logarithm (e.g., 13 digits vs. 6 digits at n=3000000 or x=1+1/3000000). - Richard R. Forberg, Jan 08 2015
Limit_{n->oo} (1/2) Sum_{j>=1} Sum_{k=1..n} ((1 - 2*k + 2*n)/((-1 + k + j*n) (k + j*n))). - Dimitri Papadopoulos, Jan 13 2016
Equals 25/27 minus lim_{x->oo} 2^(x+1)/3 - (22/27)*(4/3)^x - Zeta(Sum_{i>=1} (H_i/i^x)), letting H_i denote the i-th harmonic number. - John M. Campbell, Jan 29 2016
Limit_{x->0} -B'(x), where B(x) = -x zeta(1-x) is the "Bernoulli function". - Jean-François Alcover, May 20 2016
Sum_{k>=0} (1/2)(digamma(1/2+2^k) - digamma(2^k)) where digamma(x) = d/dx log(Gamma(x)). - Dimitri Papadopoulos, Nov 14 2016
Using the abbreviations a = log(z^2 + 1/4)/2, b = arctan(2*z) and c = cosh(Pi*z) then gamma = -Pi*Integral_{0..oo} a/c^2. The general case is for n >= 0 (which includes Euler's gamma as gamma_0) gamma_n = -(Pi/(n+1))* Integral_{0..oo} sigma(n+1)/c^2, where sigma(n) = Sum_{k=0..floor(n/2)} (-1)^k*binomial(n,2*k)*b^(2*k) *a^(n-2*k). - Peter Luschny, Apr 19 2018
Limit_{s->0} (Zeta'(1-s)*s - Zeta(1-s)) / (Zeta(1-s)*s). - Peter Luschny, Jun 18 2018
log(2) * (gamma - (1/2) * log(2)) = -Sum_{v >= 1} (1/2^(v+1)) * (Delta^v (log(w)/w))|{w=1}, where Delta(f(w)) = f(w) - f(w + 1) (forward difference). [This is a formula from Lerch (1897).] - _Petros Hadjicostas, Jul 21 2019
From Amiram Eldar, Jul 05 2020: (Start)
Equals Integral_{x=1..oo} (1/floor(x) - 1/x) dx.
Equals Integral_{x=0..1} (1/(1-x) + 1/log(x)) dx = Integral_{x=0..1} (1/x + 1/log(1-x)) dx.
Equals -Integral_{-oo..oo} x*exp(x-exp(x)) dx.
Equals Sum_{k>=1} (-1)^k * floor(log_2(k))/k.
Equals (-1/2) * Sum_{k>=1} (Lambda(k)-1)/k, where Lambda is the Mangoldt function. (End)
Equals Integral_{0..1} -1/LambertW(-1,-x*exp(-x)) dx = 1 + Integral_{0..1} LambertW(-1/x*exp(-1/x)) dx. - Gleb Koloskov, Jun 12 2021
Equals Sum_{k>=2} (-1)^k * zeta(k)/k. - Vaclav Kotesovec, Jun 19 2021
Equals lim_{x->oo} log(x) - Sum_{p prime <= x} log(p)/(p-1). - Amiram Eldar, Jun 29 2021
Limit_{n->oo} (2*HarmonicNumber(n) - HarmonicNumber(n^2)). After answer by Eric Naslund on Mathematics Stack Exchange, on Jun 21 2011. - Mats Granvik, Jul 19 2021
Equals Integral_{x=0..oo} ( exp(-x) * (1/(1-exp(-x)) - 1/x) ) dx (see Gugger or Monier). - Bernard Schott, Nov 21 2021
Equals 1/2 + Limit_{s->1} (Zeta(s) + Zeta(1/s))/2. - Thomas Ordowski, Jan 12 2023
Equals Sum_{j>=2} Sum_{k>=2} ((k-1)/(k*j^k)). - Mike Tryczak, Apr 06 2023
From Stefano Spezia, Oct 27 2024: (Start)
Equals Sum_{n>=1} n*(zeta(n+1) - 1)/(n + 1) [Euler] (see Finch at p. 30).
Equals lim_{n->oo} Sum_{prime p<=n} log(p/(p - 1)) - log(log(n)) (see Finch at p. 31). (End)
Equals lim_{s->1} zeta(s) - zeta(s)^2/zeta(2*s - 1)/2. - Mats Granvik, Jul 07 2025

A036987 Fredholm-Rueppel sequence.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 0

N. J. A. Sloane

Binary representation of the Kempner-Mahler number Sum_{k>=0} 1/2^(2^k) = A007404.
Also a(n) = A(n) mod 2 where A is any of A001700, A005573, A007854, A026641, A049027, A064063, A064088, A064090, A064092, A064325, A064327, A064329, A064331, A064613, A076026, A105523, A123273, A126694, A126930, A126931, A126982, A126983, A126987, A127016, A127053, A127358, A127360, A127361, A127363. - Philippe Deléham, May 26 2007
a(n) = (product of digits of n; n in binary notation) mod 2. This sequence is a transformation of the Thue-Morse sequence (A010060), since there exists a function f such that f(sum of digits of n) = (product of digits of n). - Ctibor O. Zizka, Feb 12 2008
a(n-1), n >= 1, the characteristic sequence for powers of 2, A000079, is the unique solution of the following formal product and formal power series identity: Product_{j>=1} (1 + a(j-1)*x^j) = 1 + Sum_{k>=1} x^k = 1/(1-x). The product is therefore Product_{l>=1} (1 + x^(2^l)). Proof. Compare coefficients of x^n and use the binary representation of n. Uniqueness follows from the recurrence relation given for the general case under A147542. - Wolfdieter Lang, Mar 05 2009
a(n) is also the number of orbits of length n for the map x -> 1-cx^2 on [-1,1] at the Feigenbaum critical value c=1.401155... . - Thomas Ward, Apr 08 2009
A054525 (Mobius transform) * A001511 = A036987 = A047999^(-1) * A001511 = the inverse of Sierpiński's gasket * the ruler sequence. - Gary W. Adamson, Oct 26 2009 [Of course this is only vaguely correct depending on how the fuzzy indexing in these formulas is made concrete. - R. J. Mathar, Jun 20 2014]
Characteristic function of A000225. - Reinhard Zumkeller, Mar 06 2012
Also parity of the Catalan numbers A000108. - Omar E. Pol, Jan 17 2012
For n >= 2, also the largest exponent k >= 0 such that n^k in binary notation does not contain both 0 and 1. Unlike for the decimal version of this sequence, A062518, where the terms are only conjectural, for this sequence the values of a(n) can be proved to be the characteristic function of A000225, as follows: n^k will contain both 0 and 1 unless n^k = 2^r-1 for some r. But this is a special case of Catalan's equation x^p = y^q-1, which was proved by Preda Mihăilescu to have no nontrivial solution except 2^3 = 3^2 - 1. - Christopher J. Smyth, Aug 22 2014
Image, under the coding a,b -> 1; c -> 0, of the fixed point, starting with a, of the morphism a -> ab, b -> cb, c -> cc. - Jeffrey Shallit, May 14 2016
Number of nonisomorphic Boolean algebras of order n+1. - Jianing Song, Jan 23 2020

			G.f. = 1 + x + x^3 + x^7 + x^15 + x^31 + x^63 + x^127 + x^255 + x^511 + ...
a(7) = 1 since 7 = 2^3 - 1, while a(10) = 0 since 10 is not of the form 2^k - 1 for any integer k.

Antti Karttunen, Table of n, a(n) for n = 0..65537
D. Bailey et al., On the binary expansions of algebraic numbers, Journal de Théorie des Nombres de Bordeaux 16 (2004), 487-518.
Paul Barry, Some observations on the Rueppel sequence and associated Hankel determinants, arXiv:2005.04066 [math.CO], 2020.
Paul Barry, Conjectures and results on some generalized Rueppel sequences, arXiv:2107.00442 [math.CO], 2021.
Daniele A. Gewurz and Francesca Merola, Sequences realized as Parker vectors of oligomorphic permutation groups, J. Integer Seqs., Vol. 6, 2003.
Mats Granvik, Mathematica program for computing Fredholm Rueppel sequences
D. Kohel, S. Ling and C. Xing, Explicit Sequence Expansions, in Sequences and their Applications, C. Ding, T. Helleseth, and H. Niederreiter, eds., Proceedings of SETA'98 (Singapore, 1998), 308-317, 1999.
Preda Mihăilescu, Primary Cyclotomic Units and a Proof of Catalan's Conjecture, J. Reine angew. Math. 572 (2004): 167-195. doi:10.1515/crll.2004.048. MR 2076124.
H. Niederreiter and M. Vielhaber, Tree Complexity and a Doubly Exponential Gap between Structured and Random Sequences, J. Complexity, 12 (1996), 187-198.
Apisit Pakapongpun and Thomas Ward, Functorial orbit counting, Journal of Integer Sequences, 12 (2009) Article 09.2.4. [From _Thomas Ward_, Apr 08 2009]
Eric Rowland and Reem Yassawi, Profinite automata, arXiv:1403.7659 [math.DS], 2014. See p. 8.
E. Sheppard, net.math post (1985)
Stephen Wolfram, [Page 1092] A New Kind of Science | Online.
Index entries for characteristic functions

Cf. A007404, A043545, A062518, A078885, A078585, A078886, A078887, A078888, A078889, A078890.
The first row of A073346. Occurs for first time in A073202 as row 6 (and again as row 8).
Congruent to any of the sequences A000108, A007460, A007461, A007463, A007464, A061922, A068068 reduced modulo 2. Characteristic function of A000225.
If interpreted with offset=1 instead of 0 (i.e., a(1)=1, a(2)=1, a(3)=0, a(4)=1, ...) then this is the characteristic function of 2^n (A000079) and as such occurs as the first row of A073265. Also, in that case the INVERT transform will produce A023359.
This is Guy Steele's sequence GS(1, 3), also GS(3, 1) (see A135416).
Cf. A054525, A047999. - Gary W. Adamson, Oct 26 2009
Cf. A043529, A127802.

a036987 n = ibp (n+1) where
   ibp 1 = 1
   ibp n = if r > 0 then 0 else ibp n' where (n',r) = divMod n 2
a036987_list = 1 : f [0,1] where f (x:y:xs) = y : f (x:xs ++ [x,x+y])
-- Same list generator function as for a091090_list, cf. A091090.
-- Reinhard Zumkeller, May 19 2015, Apr 13 2013, Mar 13 2013

A036987:= n-> `if`(2^ilog2(n+1) = n+1, 1, 0):
seq(A036987(n), n=0..128);

RealDigits[ N[ Sum[1/10^(2^n), {n, 0, Infinity}], 110]][[1]]
(* Recurrence: *)
t[n_, 1] = 1; t[1, k_] = 1;
t[n_, k_] := t[n, k] =
  If[n < k, If[n > 1 && k > 1, -Sum[t[k - i, n], {i, 1, n - 1}], 0],
   If[n > 1 && k > 1, Sum[t[n - i, k], {i, 1, k - 1}], 0]];
Table[t[n, k], {k, n, n}, {n, 104}]
(* Mats Granvik, Jun 03 2011 *)
mb2d[n_]:=1 - Module[{n2 = IntegerDigits[n, 2]}, Max[n2] - Min[n2]]; Array[mb2d, 120, 0] (* Vincenzo Librandi, Jul 19 2019 *)
Table[PadRight[{1},2^k,0],{k,0,7}]//Flatten (* Harvey P. Dale, Apr 23 2022 *)

{a(n) =( n++) == 2^valuation(n, 2)}; /* Michael Somos, Aug 25 2003 */

a(n) = !bitand(n, n+1); \\ Ruud H.G. van Tol, Apr 05 2023

from sympy import catalan
def a(n): return catalan(n)%2 # Indranil Ghosh, May 25 2017

def A036987(n): return int(not(n&(n+1))) # Chai Wah Wu, Jul 06 2022

1 followed by a string of 2^k - 1 0's. Also a(n)=1 iff n = 2^m - 1.
a(n) = a(floor(n/2)) * (n mod 2) for n>0 with a(0)=1. - Reinhard Zumkeller, Aug 02 2002 [Corrected by Mikhail Kurkov, Jul 16 2019]
Sum_{n>=0} 1/10^(2^n) = 0.110100010000000100000000000000010...
1 if n=0, floor(log_2(n+1)) - floor(log_2(n)) otherwise. G.f.: (1/x) * Sum_{k>=0} x^(2^k) = Sum_{k>=0} x^(2^k-1). - Ralf Stephan, Apr 28 2003
a(n) = 1 - A043545(n). - Michael Somos, Aug 25 2003
a(n) = -Sum_{d|n+1} mu(2*d). - Benoit Cloitre, Oct 24 2003
Dirichlet g.f. for right-shifted sequence: 2^(-s)/(1-2^(-s)).
a(n) = A000108(n) mod 2 = A001405(n) mod 2. - Paul Barry, Nov 22 2004
a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(n,k)*Sum_{j=0..k} binomial(k, 2^j-1). - Paul Barry, Jun 01 2006
A000523(n+1) = Sum_{k=1..n} a(k). - Mitch Harris, Jul 22 2011
a(n) = A209229(n+1). - Reinhard Zumkeller, Mar 07 2012
a(n) = Sum_{k=1..n} A191898(n,k)*cos(Pi*(n-1)*(k-1))/n; (conjecture). - Mats Granvik, Mar 04 2013
a(n) = A000035(A000108(n)). - Omar E. Pol, Aug 06 2013
a(n) = 1 iff n=2^k-1 for some k, 0 otherwise. - M. F. Hasler, Jun 20 2014
a(n) = ceiling(log_2(n+2)) - ceiling(log_2(n+1)). - Gionata Neri, Sep 06 2015
From John M. Campbell, Jul 21 2016: (Start)
a(n) = (A000168(n-1) mod 2).
a(n) = (A000531(n+1) mod 2).
a(n) = (A000699(n+1) mod 2).
a(n) = (A000891(n) mod 2).
a(n) = (A000913(n-1) mod 2), for n>1.
a(n) = (A000917(n-1) mod 2), for n>0.
a(n) = (A001142(n) mod 2).
a(n) = (A001246(n) mod 2).
a(n) = (A001246(n) mod 4).
a(n) = (A002057(n-2) mod 2), for n>1.
a(n) = (A002430(n+1) mod 2). (End)
a(n) = 2 - A043529(n). - Antti Karttunen, Nov 19 2017
a(n) = floor(1+log(n+1)/log(2)) - floor(log(2n+1)/log(2)). - Adriano Caroli, Sep 22 2019
This is also the decimal expansion of -Sum_{k>=1} mu(2*k)/(10^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

Edited by M. F. Hasler, Jun 20 2014

A007404 Decimal expansion of Sum_{n>=0} 1/2^(2^n).

Original entry on oeis.org

8, 1, 6, 4, 2, 1, 5, 0, 9, 0, 2, 1, 8, 9, 3, 1, 4, 3, 7, 0, 8, 0, 7, 9, 7, 3, 7, 5, 3, 0, 5, 2, 5, 2, 2, 1, 7, 0, 3, 3, 1, 1, 3, 7, 5, 9, 2, 0, 5, 5, 2, 8, 0, 4, 3, 4, 1, 2, 1, 0, 9, 0, 3, 8, 4, 3, 0, 5, 5, 6, 1, 4, 1, 9, 4, 5, 5, 5, 3, 0, 0, 0, 6, 0, 4, 8, 5, 3, 1, 3, 2, 4, 8, 3, 9, 7, 2, 6, 5, 6, 1, 7, 5, 5, 8

Offset: 0

Simon Plouffe

Kempner shows that numbers of a general form (which includes this constant) are transcendental. - Charles R Greathouse IV, Nov 07 2017

			0.81642150902189314370....

M. J. Knight, An "oceans of zeros" proof that a certain non-Liouville number is transcendental, The American Mathematical Monthly, Vol. 98, No. 10 (1991), pp. 947-949.

Harry J. Smith, Table of n, a(n) for n = 0..20000
Boris Adamczewski, The Many Faces of the Kempner Number, Journal of Integer Sequences, Vol. 16 (2013), #13.2.15.
David H. Bailey, Jonathan M. Borwein, Richard E. Crandall, and Carl Pomerance, On the Binary Expansions of Algebraic Numbers, Journal de Théorie des Nombres de Bordeaux, volume 16, number 3, 2004, pages 487-518. Also LBNL-53854 2003, and authors' copies one, four.
D. H. Bailey and H. R. P. Ferguson, Numerical results on relations between fundamental constants using a new algorithm, Mathematics of Computation, Vol.53 No. 188 (1989), 649-656. (Annotated scanned copy)
F. R. Bernhart & N. J. A. Sloane, Emails, April-May 1994
Aubrey J. Kempner, On transcendental numbers, Transactions of the American Mathematical Society 17 (1916), pp. 476-482.
Simon Plouffe, Plouffe's Inverter, sum(1/2^(2^n), n=0..infinity); to 20000 digits
Simon Plouffe, sum(1/2^(2^n), n=0..infinity) to 1024 digits
Jeffrey Shallit, Simple continued fractions for some irrational numbers. J. Number Theory 11 (1979), no. 2, 209-217.
Index entries for transcendental numbers

Cf. A007400, A078885, A078585, A078886, A078887, A078888, A078889, A078890, A036987.

RealDigits[ N[ Sum[1/2^(2^n), {n, 0, Infinity}], 110]] [[1]]

default(realprecision, 20080); x=suminf(n=0, 1/2^(2^n)); x*=10; for (n=0, 20000, d=floor(x); x=(x-d)*10; write("b007404.txt", n, " ", d)); \\ Harry J. Smith, May 07 2009

suminf(k = 0, 1/(2^(2^k))) \\ Michel Marcus, Mar 26 2017

suminf(k=0,1.>>2^k) \\ Charles R Greathouse IV, Nov 07 2017

Equals -Sum_{k>=1} mu(2*k)/(2^k - 1) = Sum_{k>=1, k odd} mu(k)/(2^k - 1). - Amiram Eldar, Jun 22 2020

Edited by Robert G. Wilson v, Dec 11 2002

Deleted old PARI program Harry J. Smith, May 20 2009

A078885 Decimal expansion of Sum {n>=0} 1/3^(2^n).

Original entry on oeis.org

4, 5, 6, 9, 4, 2, 5, 6, 2, 4, 7, 7, 6, 3, 9, 6, 6, 1, 1, 1, 5, 4, 9, 1, 8, 2, 6, 1, 6, 6, 9, 0, 3, 0, 3, 7, 9, 8, 9, 9, 4, 2, 5, 9, 9, 7, 1, 3, 8, 3, 1, 1, 9, 2, 0, 9, 1, 0, 5, 6, 8, 7, 4, 3, 0, 9, 9, 8, 2, 4, 1, 8, 2, 9, 9, 6, 9, 0, 0, 2, 9, 5, 1, 8, 8, 2, 5, 1, 5, 2, 6, 6, 8, 0, 6, 8, 7, 7, 5, 3, 3, 4, 5, 2, 5

Offset: 0

Robert G. Wilson v, Dec 11 2002

			0.456942562477639661115491826166903037989942599713831192091056874309982...

Harry J. Smith, Table of n, a(n) for n = 0..20000
Aubrey J. Kempner, On Transcendental Numbers, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
Index entries for transcendental numbers

Cf. A004200 (continued fraction), A011764.

Similar sums: A007404, A078585, A078886, A078887, A078888, A078889, A078890, A036987.

RealDigits[ N[ Sum[1/3^(2^n), {n, 0, Infinity}], 110]] [[1]]

default(realprecision, 20080); x=suminf(n=0, 1/3^(2^n)); x*=10; for (n=0, 20000, d=floor(x); x=(x-d)*10; write("b078885.txt", n, " ", d)); \\ Harry J. Smith, May 10 2009

Equals -Sum_{k>=1} mu(2*k)/(3^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

A078886 Decimal expansion of Sum {n>=0} 1/5^(2^n).

Original entry on oeis.org

2, 4, 1, 6, 0, 2, 5, 6, 0, 0, 0, 6, 5, 5, 3, 6, 0, 0, 0, 0, 0, 0, 4, 2, 9, 4, 9, 6, 7, 2, 9, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 8, 4, 4, 6, 7, 4, 4, 0, 7, 3, 7, 0, 9, 5, 5, 1, 6, 1, 6, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 4, 0, 2, 8, 2, 3, 6, 6, 9, 2, 0, 9, 3, 8, 4

Offset: 0

Robert G. Wilson v, Dec 11 2002

Decimal expansion has increasingly large gaps of zeros, the digits delimited by these zeros are equal to 2^(2^m) as m=0,1,2,3,... The continued fraction expansion (A122165) and consists entirely of 3's, 5's and 7's, after an initial partial quotient of 4. - Paul D. Hanna, Aug 22 2006

			0.241602560006553600000...
From _Paul D. Hanna_, Aug 22 2006: (Start)
Decimal expansion consists of large gaps of zeros between strings of digits that form powers of 2; this can be seen by grouping the digits as follows:
x = .2 4 16 0 256 000 65536 000000 4294967296 000000000000 ...= 0.24160256000655360000004294...
and then recognizing the substrings as powers of 2:
2 = 2^(2^0), 4 = 2^(2^1), 16 = 2^(2^2), 65536 = 2^(2^4), 4294967296 = 2^(2^5), 18446744073709551616 = 2^(2^6), ... (End)

Aubrey J. Kempner, On Transcendental Numbers, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
Index entries for transcendental numbers

Cf. A122165 (continued fraction), A176594.

Similar sums: A007404, A078885, A078585, A078887, A078888, A078889, A078890, A036987.

RealDigits[ N[ Sum[1/5^(2^n), {n, 0, Infinity}], 110]][[1]]

{a(n)=local(x=sum(k=0,ceil(3+log(n+1)),1/5^(2^k)));(floor(10^n*x))%10} \\ Paul D. Hanna, Aug 22 2006

Equals -Sum_{k>=1} mu(2*k)/(5^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

Edited by R. J. Mathar, Aug 02 2008

A078887 Decimal expansion of Sum {n>=0} 1/6^(2^n).

Original entry on oeis.org

1, 9, 5, 2, 1, 6, 6, 4, 4, 7, 5, 7, 2, 5, 1, 2, 8, 4, 9, 2, 5, 1, 0, 5, 1, 0, 6, 3, 5, 1, 5, 2, 1, 9, 4, 8, 4, 3, 2, 2, 4, 3, 4, 6, 8, 9, 9, 3, 2, 0, 3, 7, 2, 9, 8, 0, 7, 9, 2, 3, 1, 7, 4, 2, 6, 7, 3, 0, 3, 5, 8, 8, 3, 7, 2, 1, 2, 7, 6, 9, 0, 9, 0, 0, 4, 8, 7, 8, 5, 6, 1, 4, 9, 1, 6, 2, 4, 4, 6, 3, 1, 3, 6, 2, 1

Offset: 0

Robert G. Wilson v, Dec 11 2002

			0.195216644757251284925...

Aubrey J. Kempner, On Transcendental Numbers, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
Index entries for transcendental numbers

Cf. A165424.

Similar sums: A007404, A078885, A078585, A078886, A078888, A078889, A078890, A036987.

RealDigits[ N[ Sum[1/6^(2^n), {n, 0, Infinity}], 110]][[1]]

suminf(n=0, 1/6^(2^n)) \\ Michel Marcus, Nov 11 2020

Equals -Sum_{k>=1} mu(2*k)/(6^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

A078888 Decimal expansion of Sum {n>=0} 1/7^(2^n).

Original entry on oeis.org

1, 6, 3, 6, 8, 1, 9, 7, 2, 7, 1, 6, 8, 6, 8, 0, 1, 7, 9, 1, 1, 7, 2, 9, 7, 2, 5, 8, 9, 3, 9, 0, 9, 2, 0, 0, 6, 0, 5, 2, 4, 4, 8, 5, 4, 1, 5, 9, 3, 3, 6, 8, 2, 5, 3, 2, 7, 8, 6, 2, 2, 1, 0, 3, 5, 9, 7, 2, 5, 1, 1, 8, 5, 9, 2, 9, 2, 3, 5, 7, 5, 0, 2, 5, 1, 1, 7, 3, 9, 7, 8, 4, 0, 1, 2, 7, 2, 9, 4, 3, 8, 1, 8, 4, 7

Offset: 0

Robert G. Wilson v, Dec 11 2002

			0.163681972716868017911...

Aubrey J. Kempner, On Transcendental Numbers, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
Index entries for transcendental numbers

Cf. A165425.

Similar sums: A007404, A078885, A078585, A078886, A078887, A078889, A078890, A036987.

RealDigits[ N[ Sum[1/7^(2^n), {n, 0, Infinity}], 110]][[1]]

suminf(n=0, 1/7^(2^n)) \\ Michel Marcus, Nov 11 2020

Equals -Sum_{k>=1} mu(2*k)/(7^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

A078889 Decimal expansion of Sum {n>=0} 1/8^(2^n).

Original entry on oeis.org

1, 4, 0, 8, 6, 9, 2, 0, 0, 2, 2, 9, 6, 4, 8, 3, 2, 8, 1, 0, 4, 3, 0, 3, 8, 0, 0, 5, 1, 3, 5, 5, 1, 1, 3, 0, 1, 0, 4, 8, 7, 4, 0, 7, 9, 5, 1, 1, 5, 8, 7, 6, 5, 7, 0, 4, 4, 6, 8, 3, 8, 8, 8, 8, 6, 5, 8, 8, 4, 5, 4, 8, 1, 8, 9, 4, 4, 7, 2, 5, 6, 1, 1, 6, 1, 0, 1, 2, 3, 4, 0, 7, 1, 1, 8, 4, 1, 1, 0, 4, 5, 5, 5, 1, 9

Offset: 0

Robert G. Wilson v, Dec 11 2002

			0.140869200229648328104...

Aubrey J. Kempner, On Transcendental Numbers, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
Index entries for transcendental numbers

Cf. A165426.

Similar sums: A007404, A078885, A078585, A078886, A078887, A078888, A078890, A036987.

RealDigits[ N[ Sum[1/8^(2^n), {n, 0, Infinity}], 110]][[1]]

suminf(n=0, 1/8^(2^n)) \\ Michel Marcus, Nov 11 2020

Equals -Sum_{k>=1} mu(2*k)/(8^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

A078890 Decimal expansion of Sum {n>=0} 1/9^(2^n).

Original entry on oeis.org

1, 2, 3, 6, 0, 9, 2, 2, 9, 1, 4, 4, 3, 0, 6, 3, 2, 7, 7, 8, 2, 1, 5, 8, 4, 9, 2, 8, 3, 3, 5, 6, 9, 7, 0, 4, 6, 5, 6, 6, 0, 9, 2, 6, 6, 3, 8, 0, 4, 9, 7, 8, 5, 8, 7, 5, 7, 7, 2, 3, 5, 4, 0, 9, 7, 6, 6, 4, 9, 0, 8, 4, 9, 6, 6, 3, 5, 6, 6, 9, 6, 1, 8, 5, 4, 9, 1, 8, 1, 9, 3, 3, 4, 7, 3, 5, 4, 4, 2, 0, 0, 1, 1, 9, 1

Offset: 0

Robert G. Wilson v, Dec 11 2002

			0.123609229144306327782...

Aubrey J. Kempner, On Transcendental Numbers, Transactions of the American Mathematical Society, volume 17, number 4, October 1916, pages 476-482.
Index entries for transcendental numbers

Similar sums: A007404, A078885, A078585, A078886, A078887, A078888, A078889, A036987.

RealDigits[ N[ Sum[1/9^(2^n), {n, 0, Infinity}], 110]][[1]]

suminf(n=0, 1/9^(2^n)) \\ Michel Marcus, Nov 11 2020

Equals A078885 - 1/3 = A078885 - A010701. - R. J. Mathar, Apr 23 2009

Equals -Sum_{k>=1} mu(2*k)/(9^k - 1), where mu is the Möbius function (A008683). - Amiram Eldar, Jul 12 2020

A076214 Decimal expansion of C = Sum_{k>=0} 1/2^(2^k-1).

Original entry on oeis.org

1, 6, 3, 2, 8, 4, 3, 0, 1, 8, 0, 4, 3, 7, 8, 6, 2, 8, 7, 4, 1, 6, 1, 5, 9, 4, 7, 5, 0, 6, 1, 0, 5, 0, 4, 4, 3, 4, 0, 6, 6, 2, 2, 7, 5, 1, 8, 4, 1, 1, 0, 5, 6, 0, 8, 6, 8, 2, 4, 2, 1, 8, 0, 7, 6, 8, 6, 1, 1, 1, 2, 2, 8, 3, 8, 9, 1, 1, 0, 6, 0, 0, 1, 2, 0, 9, 7, 0, 6, 2, 6, 4, 9, 6, 7, 9, 4, 5, 3, 1, 2, 3, 5, 1, 1

Offset: 1

Benoit Cloitre, Nov 03 2002

This constant has a nice continued fraction expansion (i.e. only 1 and 2 occur). C arises when looking for a sequence b(n) such that : b(1) = 0, b(n+1) is the smallest integer > b(n) such that the continued fraction for 1/2^b(1) + 1/2^b(2) + ... + 1/2^b(n+1) contains only 1's or 2's. Because b(n) = 2^n-1 and C = Sum_{k>=0} 1/2^b(k).

			1.632843018043786287416159475061050443406622751841105608682421807686111...

Harry J. Smith, Table of n, a(n) for n = 1..20000
Boris Adamczewski, The Many Faces of the Kempner Number, Journal of Integer Sequences, Vol. 16 (2013), Article 13.2.15.
Michael Ian Shamos, Property Enumerators and a Partial Sum Theorem, 2011; alternative link.

Cf. A006466 (continued fraction), A007404, A078585.

Take[ RealDigits[ 2*NSum[1/2^2^k, {k, 0, Infinity}, WorkingPrecision -> 120]][[1]], 105] (* Jean-François Alcover, Nov 15 2011 *)

default(realprecision, 20080); x=suminf(k=0, 1/2^(2^k)); x*=2; for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b076214.txt", n, " ", d)); \\ Harry J. Smith, May 09 2009

Equals 2 * Sum_{k>=0} 1/2^(2^k) = 2 * A007404. - Harry J. Smith, May 09 2009
From Amiram Eldar, Mar 12 2024: (Start)
Equals 1 + 2 * A078585.
Equals 1 + Sum_{k>=1} floor(log_2(k))/2^k (Shamos, 2011, p. 8). (End)

cp's OEIS Frontend

A001620 Decimal expansion of Euler's constant (or the Euler-Mascheroni constant), gamma.

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A036987 Fredholm-Rueppel sequence.

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A007404 Decimal expansion of Sum_{n>=0} 1/2^(2^n).

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A078885 Decimal expansion of Sum {n>=0} 1/3^(2^n).

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A078886 Decimal expansion of Sum {n>=0} 1/5^(2^n).

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A078887 Decimal expansion of Sum {n>=0} 1/6^(2^n).

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