cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Previous Showing 41-50 of 263 results. Next

A016578 Decimal expansion of log(3/2).

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			0.4054651081081643819780131154643491365719904234624941976140143...
		

References

  • L. B. W. Jolley, Summation of Series, Dover (1961), eq (102), page 20.

Crossrefs

Programs

  • Mathematica
    RealDigits[Log[3/2],10,111][[1]] (* Robert G. Wilson v, Aug 08 2011 *)
  • PARI
    default(realprecision, 20080); x=10*log(3/2); for (n=0, 20000, d=floor(x); x=(x-d)*10; write("b016578.txt", n, " ", d)); \\ Harry J. Smith, May 17 2009

Formula

Equals Sum {k>=1} 1/(k*3^k). - Robert G. Wilson v, Aug 08 2011
Equals 1/2 - 1/(2*2^2) + 1/(3*2^3) - 1/(4*2^4) + ... [Jolley].
Equals A002391-A002162. - Michel Marcus, Sep 17 2016
From Amiram Eldar, Aug 07 2020: (Start)
Equals 2 * arctanh(1/5).
Equals Integral_{x=0..oo} 1/(2*exp(x) + 1) dx. (End)
log(3/2) = 2*Sum_{n >= 1} 1/(n*P(n, 5)*P(n-1, 5)), where P(n, x) denotes the n-th Legendre polynomial. The first 10 terms of the series gives the approximation log(3/2) = 0.40546510810816438197(04...), correct to 20 decimal places. - Peter Bala, Mar 16 2024
Equals Sum_{n >= 1} (-1)^(n+1) * 5/(n*binomial(2*n, n)*6^n). The n-th term of the series is O(5*sqrt(Pi/n)*1/24^n). - Peter Bala, Mar 04 2025
Equals Integral_{x=0..1} (sqrt(x) - 1)/log(x) dx. - Kritsada Moomuang, Jun 14 2025

A016730 Continued fraction for log(2).

Original entry on oeis.org

0, 1, 2, 3, 1, 6, 3, 1, 1, 2, 1, 1, 1, 1, 3, 10, 1, 1, 1, 2, 1, 1, 1, 1, 3, 2, 3, 1, 13, 7, 4, 1, 1, 1, 7, 2, 4, 1, 1, 2, 5, 14, 1, 10, 1, 4, 2, 18, 3, 1, 4, 1, 6, 2, 7, 3, 3, 1, 13, 3, 1, 4, 4, 1, 3, 1, 1, 1, 1, 2, 17, 3, 1, 2, 32, 1, 1, 1
Offset: 0

Views

Author

Keywords

Comments

Continued fraction for 1/log(2) is the same but without the initial zero.

Examples

			log(2) = 0.6931471805599453094... = 0 + 1/(1 + 1/(2 + 1/(3 + 1/(1 + ...)))). - _Harry J. Smith_, Apr 21 2009
		

Crossrefs

Cf. A120754, A120755, A002162 (decimal expansion).

Programs

  • Magma
    ContinuedFraction(Log(2)); // G. C. Greubel, Sep 15 2018
  • Mathematica
    ContinuedFraction[Log[2], 80] (* Alonso del Arte, Oct 03 2017 *)
  • PARI
    { allocatemem(932245000); default(realprecision, 21000); x=contfrac(log(2)); for (n=1, 20000, write("b016730.txt", n-1, " ", x[n])); } \\ Harry J. Smith, Apr 21 2009
    

Extensions

Offset changed by Andrew Howroyd, Jul 10 2024

A094642 Decimal expansion of log(Pi/2).

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			log(Pi/2) = 0.45158270528945486472619522989488214357179467855505...
		

References

  • George Boros and Victor Moll, Irresistible Integrals: Symbolics, Analysis and Experiments in the Evaluation of Integrals, Cambridge University Press, Cambridge, 2004, Chap. 7.
  • Jonathan Borwein and Peter Borwein, Pi and the AGM, John Wiley & Sons, New York, 1987, Chap. 11.
  • Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, 2003, Section 1.6.3, pp. 43-44.

Crossrefs

Programs

Formula

Equals Sum_{n>=1} zeta(2*n)/(n*2^(2*n)) (cf. Boros & Moll p. 131). - Jean-François Alcover, Apr 29 2013
Equals Re(log(log(I))). - Stanislav Sykora, May 09 2015
Equals Integral_{-oo..+oo} -log(1/2 + i*z)/cosh(Pi*z) dz, where i is the imaginary unit. - Peter Luschny, Apr 08 2018
Equals Integral_{0..Pi/2} (2/(Pi-2*t)-tan(t)) dt. - Clark Kimberling, Jul 10 2020
Equals -Sum_{k>=1} log(1 - 1/(2*k)^2). - Amiram Eldar, Aug 12 2020
Equals Sum_{k>=1} (-1)^(k+1) * log(1 + 1/k). - Amiram Eldar, Jun 26 2021
Equals A053510 - A002162. - R. J. Mathar, Jun 15 2023

A099974 Write log(2) as a binary fraction; read this from left to right and whenever a 1 appears, note the integer formed by reading leftwards from that 1.

Original entry on oeis.org

1, 5, 13, 141, 653, 1677, 3725, 20109, 544397, 2641549, 6835853, 15224461, 32001677, 65556109, 132664973, 266882701, 803753613, 1877495437, 4024979085, 8319946381, 16909880973, 51269619341, 601025433229, 1700537061005
Offset: 0

Views

Author

N. J. A. Sloane, Nov 13 2004, based on correspondence from Artur Jasinski, Mar 25 2003

Keywords

Examples

			log(2) = 0.69314718055994530941723212145817656807550013436025525412... = 0.1011000101110010000101111111011111010001110011110111100110101011110010011110... in binary.
		

Crossrefs

Programs

  • Mathematica
    d = 100; l = First[RealDigits[N[Log[2], d], 2]]; Do[m = Take[l, n]; k = Length[m]; If[m[[k]] == 1, Print[FromDigits[Reverse[m], 2]]], {n, 1, d}] (* Ryan Propper, Aug 17 2005 *)
    Module[{nn=50,l2},l2=RealDigits[Log[2],2,nn][[1]];Table[FromDigits[ Reverse[ Take[ l2,n]],2],{n,nn}]]//Union (* Harvey P. Dale, Mar 29 2016 *)

Extensions

More terms from Ryan Propper, Aug 17 2005

A242023 Decimal expansion of Sum_{n >= 1} (-1)^(n + 1)*24/(n*(n + 1)*(n + 2)*(n + 3)).

Original entry on oeis.org

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

Views

Author

Richard R. Forberg, Aug 11 2014

Keywords

Comments

Sum of terms of the inverse of Binomial(n,4) or A000332, for n>=4, with alternating signs.
In general the sums of Binomial coefficients of this form appear to have the form m*log(2) - r, where m is an integer and r is rational as below:
For Binomial(n,1): m = 1, r = 0. See A002162.
For Binomial(n,2): m = 4, r = 2. See A000217.
For Binomial(n,3): m = 12 r = 15/2. See A000292.
For Binomial(n,4): m = 32, r = 64/3. See A000332.
For Binomial(n,5): m = 80, r = 655/12. See A000389.
For Binomial(n,6): m = 192, r = 661/5. See A000579.
For Binomial(n,7): m = 448, r = 9289/30. See A000580.
For Binomial(n,8): m = 1024, r = 74432/105. See A000581.
This is generalized as follows:
m grows as A001787(k) = k*2^(k-1) for Binomial(n,k).
r * (k-1)! produces the integer sequence: a(k) = 0, 2, 15, 128, 1310, 15864, 222936, 3572736, where a(k+1)/a(k) approaches 2*k for large k.
Results are precise to 100 digits or more using Mathematica.

Examples

			0.8473764445849165680180945...
		

Crossrefs

Programs

  • Magma
    [32*Log(2) - 64/3]; // G. C. Greubel, Nov 23 2017
  • Mathematica
    Sum[N[(-1)^(n + 1)*24/(n*(n + 1)*(n + 2)*(n + 3)), 150], {n, 1, Infinity}]
    RealDigits[32*Log[2] - 64/3, 10, 50][[1]] (* G. C. Greubel, Nov 23 2017 *)
  • PARI
    32*log(2) - 64/3 \\ Michel Marcus, Aug 13 2014
    
  • PARI
    sumalt(n=1, (-1)^(n + 1)*24/(n*(n + 1)*(n + 2)*(n + 3))) \\ Michel Marcus, Aug 14 2014
    

Formula

Equals 32*log(2) - 64/3.
Equals 32*(A259284-1). - R. J. Mathar, Jun 30 2021

A267316 Decimal expansion of the Dirichlet eta function at 5.

Original entry on oeis.org

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

Views

Author

Ilya Gutkovskiy, Jan 13 2016

Keywords

Examples

			1/1^5 - 1/2^5 + 1/3^5 - 1/4^5 + 1/5^5 - 1/6^5 + ... = 0.972119770446909305935655143553469532553513362...
		

Crossrefs

Cf. A002162 (value at 1), A013663, A072691 (value at 2), A197070 (value at 3), A267315 (value at 4), A136676, A334604.

Programs

  • Mathematica
    RealDigits[(15 Zeta[5])/16, 10, 120][[1]]
  • PARI
    15*zeta(5)/16 \\ Michel Marcus, Feb 01 2016
    
  • Sage
    s = RLF(0); s
    RealField(110)(s)
    for i in range(1, 10000): s += -((-1)^i/((i)^5))
    print(s) # Terry D. Grant, Aug 05 2016

Formula

Equals Sum_{k > 0} (-1)^(k+1)/k^5 = (15*zeta(5))/16.
Equals Lim_{n -> infinity} A136676(n)/A334604(n). - Petros Hadjicostas, May 07 2020

A016639 Decimal expansion of log(16) = 4*log(2).

Original entry on oeis.org

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

Views

Author

Keywords

Examples

			2.77258872223978123766892848583270627230200053744102101648272... - _Harry J. Smith_, May 17 2009
		

References

  • M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 2.

Crossrefs

Equals 4*A002162.
Equals (4/5)*A016655.
Equals A303658 + 2.
Cf. A016444 (continued fraction).

Programs

  • Magma
    Log(16); // Vincenzo Librandi, Feb 20 2015
  • Mathematica
    RealDigits[Log[16], 10, 120][[1]] (* Harvey P. Dale, Jun 12 2012 *)
  • PARI
    default(realprecision, 20080); x=log(16); for (n=1, 20000, d=floor(x); x=(x-d)*10; write("b016639.txt", n, " ", d)); \\ Harry J. Smith, May 17 2009, corrected May 19 2009
    

Formula

Equals 4*A002162.
Equals Sum_{k=1..4} (-1)^(k+1) gamma(0, k/4) where gamma(n,x) denotes the generalized Stieltjes constants. - Peter Luschny, May 16 2018
Equals -2 + Sum_{k>=1} H(k)*(k+1)/2^k, where H(k) = A001008(k)/A002805(k) is the k-th harmonic number. - Amiram Eldar, May 28 2021
Equals 1 + Limit_{n -> infinity} (1/n)*Sum_{k = 1..n} (2*n + k)/(2*n - k) = 2*( 1 + Limit_{n -> infinity} (1/n)*Sum_{k = 1..n} (n - k)/(n + k) ). - Peter Bala, Oct 10 2021
Equals 2 + 1/(1 + 1/(3 + 2/(4 + 6/(5 + 6/(6 + 12/(7 + 12/(8 + ... + n*(n-1)/(2*n-1 + n*(n-1)/(2*n + ...))))))))). Cf. A188859. - Peter Bala, Mar 04 2024

A086054 Decimal expansion of Pi*log(2).

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, Jul 07 2003

Keywords

Comments

Madelung constant b2(2), negated.

Examples

			2.1775860903036021305006888982376139...
		

References

  • G. Boros and V. H. Moll, Irresistible Integrals: Symbolics, Analysis and Experiments in the Evaluation of Integrals, Cambridge University Press, 2004 (equation 13.6.6).

Crossrefs

Cf. A000796 (Pi), A002162 (log(2)), A173623.

Programs

  • Mathematica
    RealDigits[Pi Log[2],10,120][[1]] (* Harvey P. Dale, Dec 31 2011 *)

Formula

Pi*log(2) = -(8/3)*int(log(x)/sqrt(1+4*x-4*x^2), x=0..1). - John M. Campbell, Feb 07 2012
Pi*log(2) = int((x/sin(x))^2, x=0..Pi/2) = int(log(x^2+1)/(x^2+1), x=0..infinity) = int(-log(cos(x)), x=-Pi/2..Pi/2) = int(arctan(1/x)^2, x=0..infinity). - Jean-François Alcover, May 30 2013
From Amiram Eldar, Jul 11 2020: (Start)
Equals Integral_{x=-1..1} arcsin(x) dx / x.
Equals Integral_{x=-Pi/2..Pi/2} x*cot(x) dx. (End)
Equals Integral_{x = 0..oo} log(x^2 + 4)/(x^2 + 4) dx. - Peter Bala, Jul 22 2022
Equals -Im(Polylog(2, 2)). - Mohammed Yaseen, Jul 03 2024

Extensions

Corrected by Antti Ahti (antti.ahti(AT)tkk.fi), Nov 17 2004
More terms from Benoit Cloitre, May 21 2005

A118858 Decimal expansion of log(2)/Pi^2.

Original entry on oeis.org

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

Views

Author

Eric W. Weisstein, May 02 2006

Keywords

Examples

			0.07023049277268287640...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[Log[2]/Pi^2, 10, 100][[1]] (* Amiram Eldar, Jun 25 2021 *)
  • PARI
    log(2)/Pi^2 \\ Michel Marcus, Jun 25 2021

Formula

Equals lim_{n->oo} A328499(n)/n. - Amiram Eldar, Jun 25 2021
Equals Integral_{z>=0} z*sech(Pi*z)^2. - Peter Luschny, Aug 03 2021

A187832 Decimal expansion of integral from 1/2 to 1 of (1-x)/x dx.

Original entry on oeis.org

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

Views

Author

Robert G. Wilson v, Dec 27 2012

Keywords

Comments

Replacing 1/2 with any other number 0 < t < 1, the value of the integral is t - 1 - log(t).

Examples

			0.193147180559945309417232121458176568075500134360255254120680009493393621969...
		

References

  • J.-M. Monier, Cours, Analyse, Tome 4, 2ème année, MP.PSI.PC.PT, Dunod, 1997, Exercice 4.3.14 pages 53 and 367.

Crossrefs

Apart from the first digit the same as A002162.
Cf. A239354: Sum_{k>=1} 1/((2k)*(2k+1)*(2k+2)).

Programs

Formula

Equals log(2) - 1/2 = A002162 - 1/2.
Equals Sum_{k>=1} 1/((2k-1)*(2k)*(2k+1)). - Bruno Berselli, Mar 16 2014
From Amiram Eldar, Jul 28 2020: (Start)
Equals Sum_{k>=0} (-1)^k/(k+3).
Equals Sum_{k>=2} 1/(k * 2^k).
Equals Sum_{k>=2} 1/(4*k^2 - 2*k).
Equals Sum_{k>=2} (zeta(k) - 1)/2^k.
Equals Sum_{k>=1} zeta(2*k + 1)/2^(2*k + 1). (End)
From Bernard Schott, Nov 22 2021: (Start)
Equals Sum_{k>=1} (S(k) - log(2)) when S(k) = Sum_{m=1..k} (-1)^(m+1) / m.
Equals Integral_{x=0..1} x/(1+x)^2 dx. (End)
Equals Sum_{k,m>=1} (-1)^(k+m)/(k+m). - Amiram Eldar, Jun 09 2022
Equals Integral_{x = 0..1} Integral_{y = 0..1} x*y/(x + y)^2 dy dx. - Peter Bala, Dec 12 2022
Previous Showing 41-50 of 263 results. Next