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.

Showing 1-8 of 8 results.

A001113 Decimal expansion of e.

Original entry on oeis.org

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

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Author

Keywords

Comments

e is sometimes called Euler's number or Napier's constant.
Also, decimal expansion of sinh(1)+cosh(1). - Mohammad K. Azarian, Aug 15 2006
If m and n are any integers with n > 1, then |e - m/n| > 1/(S(n)+1)!, where S(n) = A002034(n) is the smallest number such that n divides S(n)!. - Jonathan Sondow, Sep 04 2006
Limit_{n->infinity} A000166(n)*e - A000142(n) = 0. - Seiichi Kirikami, Oct 12 2011
Euler's constant (also known as Euler-Mascheroni constant) is gamma = 0.57721... and Euler's number is e = 2.71828... . - Mohammad K. Azarian, Dec 29 2011
One of the many continued fraction expressions for e is 2+2/(2+3/(3+4/(4+5/(5+6/(6+ ... from Ramanujan (1887-1920). - Robert G. Wilson v, Jul 16 2012
e maximizes the value of x^(c/x) for any real positive constant c, and minimizes for it for a negative constant, on the range x > 0. This explains why elements of A000792 are composed primarily of factors of 3, and where needed, some factors of 2. These are the two primes closest to e. - Richard R. Forberg, Oct 19 2014
There are two real solutions x to c^x = x^c when c, x > 0 and c != e, one of which is x = c, and only one real solution when c = e, where the solution is x = e. - Richard R. Forberg, Oct 22 2014
This is the expected value of the number of real numbers that are independently and uniformly chosen at random from the interval (0, 1) until their sum exceeds 1 (Bush, 1961). - Amiram Eldar, Jul 21 2020

Examples

			2.71828182845904523536028747135266249775724709369995957496696762772407663...
		

References

  • Florian Cajori, A History of Mathematical Notations, Dover edition (2012), par. 400.
  • John H. Conway and Richard K. Guy, The Book of Numbers, New York: Springer-Verlag, 1996. See pp. 24, 250-256.
  • Steven R. Finch, Mathematical Constants, Cambridge, 2003, Section 1.3.
  • Jan Gullberg, Mathematics from the Birth of Numbers, W. W. Norton & Co., NY & London, 1997, §3.4 Irrational Numbers, p. 85.
  • E. Maor, e: The Story of a Number, Princeton Univ. Press, 1994.
  • Clifford A. Pickover, A Passion for Mathematics, Wiley, 2005; see p. 52.
  • G. W. Reitwiesner, An ENIAC determination of pi and e to more than 2000 decimal places. Math. Tables and Other Aids to Computation 4, (1950). 11-15.
  • 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, chapters 1 and 2, equations 1:7:4, 2:5:4 at pages 13, 20.
  • David Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, Revised edition 1987. See p. 46.

Crossrefs

Cf. A002034, A003417 (continued fraction), A073229, A122214, A122215, A122216, A122217, A122416, A122417.
Expansion of e in base b: A004593 (b=2), A004594 (b=3), A004595 (b=4), A004596 (b=5), A004597 (b=6), A004598 (b=7), A004599 (b=8), A004600 (b=9), this sequence (b=10), A170873 (b=16). - Jason Kimberley, Dec 05 2012
Powers e^k: A092578 (k = -7), A092577 (k = -6), A092560 (k = -5), A092553 - A092555 (k = -2 to -4), A068985 (k = -1), A072334 (k = 2), A091933 (k = 3), A092426 (k = 4), A092511 - A092513 (k = 5 to 7).

Programs

  • Haskell
    -- See Niemeijer link.
    a001113 n = a001113_list !! (n-1)
    a001113_list = eStream (1, 0, 1)
       [(n, a * d, d) | (n, d, a) <- map (\k -> (1, k, 1)) [1..]] where
       eStream z xs'@(x:xs)
         | lb /= approx z 2 = eStream (mult z x) xs
         | otherwise = lb : eStream (mult (10, -10 * lb, 1) z) xs'
         where lb = approx z 1
               approx (a, b, c) n = div (a * n + b) c
               mult (a, b, c) (d, e, f) = (a * d, a * e + b * f, c * f)
    -- Reinhard Zumkeller, Jun 12 2013
  • Maple
    Digits := 200: it := evalf((exp(1))/10, 200): for i from 1 to 200 do printf(`%d,`,floor(10*it)): it := 10*it-floor(10*it): od: # James Sellers, Feb 13 2001
  • Mathematica
    RealDigits[E, 10, 120][[1]] (* Harvey P. Dale, Nov 14 2011 *)

Formula

e = Sum_{k >= 0} 1/k! = lim_{x -> 0} (1+x)^(1/x).
e is the unique positive root of the equation Integral_{u = 1..x} du/u = 1.
exp(1) = ((16/31)*(1 + Sum_{n>=1} ((1/2)^n*((1/2)*n^3 + (1/2)*n + 1)/n!)))^2. Robert Israel confirmed that the above formula is correct, saying: "In fact, Sum_{n=0..oo} n^j*t^n/n! = P_j(t)*exp(t) where P_0(t) = 1 and for j >= 1, P_j(t) = t (P_(j-1)'(t) + P_(j-1)(t)). Your sum is 1/2*P_3(1/2) + 1/2*P_1(1/2) + P_0(1/2)." - Alexander R. Povolotsky, Jan 04 2009
exp(1) = (1 + Sum_{n>=1} ((1+n+n^3)/n!))/7. - Alexander R. Povolotsky, Sep 14 2011
e = 1 + (2 + (3 + (4 + ...)/4)/3)/2 = 2 + (1 + (1 + (1 + ...)/4)/3)/2. - Rok Cestnik, Jan 19 2017
From Peter Bala, Nov 13 2019: (Start)
The series representation e = Sum_{k >= 0} 1/k! is the case n = 0 of the more general result e = n!*Sum_{k >= 0} 1/(k!*R(n,k)*R(n,k+1)), n = 0,2,3,4,..., where R(n,x) is the n-th row polynomial of A269953.
e = 2 + Sum_{n >= 0} (-1)^n*(n+2)!/(d(n+2)*d(n+3)), where d(n) = A000166(n).
e = Sum_{n >= 0} (x^2 + (n+2)*x + n)/(n!(n + x)*(n + 1 + x)), provided x is not zero or a negative integer. (End)
Equals lim_{n -> oo} (2*3*5*...*prime(n))^(1/prime(n)). - Peter Luschny, May 21 2020
e = 3 - Sum_{n >= 0} 1/((n+1)^2*(n+2)^2*n!). - Peter Bala, Jan 13 2022
e = lim_{n->oo} prime(n)*(1 - 1/n)^prime(n). - Thomas Ordowski, Jan 31 2023
e = 1+(1/1)*(1+(1/2)*(1+(1/3)*(1+(1/4)*(1+(1/5)*(1+(1/6)*(...)))))), equivalent to the first formula. - David Ulgenes, Dec 01 2023
From Michal Paulovic, Dec 12 2023: (Start)
Equals lim_{n->oo} (1 + 1/n)^n.
Equals x^(x^(x^...)) (infinite power tower) where x = e^(1/e) = A073229. (End)
Equals Product_{k>=1} (1 + 1/k) * (1 - 1/(k + 1)^2)^k. - Antonio Graciá Llorente, May 14 2024
Equals lim_{n->oo} Product_{k=1..n} (n^2 + k)/(n^2 - k) (see Finch). - Stefano Spezia, Oct 19 2024
e ~ (1 + 9^((-4)^(7*6)))^(3^(2^85)), correct to more than 18*10^24 digits (Richard Sabey, 2004); see Haran and Grime link. - Paolo Xausa, Dec 21 2024.

A105793 Expansion of e.g.f. (1 + y)^(1 + x).

Original entry on oeis.org

1, 1, 1, 0, 1, 1, 0, -1, 0, 1, 0, 2, -1, -2, 1, 0, -6, 5, 5, -5, 1, 0, 24, -26, -15, 25, -9, 1, 0, -120, 154, 49, -140, 70, -14, 1, 0, 720, -1044, -140, 889, -560, 154, -20, 1, 0, -5040, 8028, -64, -6363, 4809, -1638, 294, -27, 1, 0, 40320, -69264, 8540, 50840, -44835, 17913, -3990, 510, -35, 1
Offset: 0

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Author

Paul Barry, Apr 20 2005

Keywords

Comments

Generalized Stirling number triangle of first kind. Row sums are (1,2,2,0,0,0,...) = 2C(2,n) - 2C(1,n) + C(0,n). Inverse is A105794.
Triangle T(n,k), 0 <= k <= n, read by rows, given by [1, -1, 0, -2, -1, -3, -2, -4, -3, -5, -4, -6, ...] DELTA [1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, ...] where DELTA is the operator defined in A084938. - Philippe Deléham, Aug 23 2006

Examples

			From _Wolfdieter Lang_, Jun 19 2017: (Start)
The triangle T(n, k) starts
  n\k  0     1      2    3     4      5     6     7   8   9 10 ...
  0:   1
  1:   1     1
  2:   0     1      1
  3:   0    -1      0    1
  4:   0     2     -1   -2     1
  5:   0    -6      5    5    -5      1
  6:   0    24    -26  -15    25     -9     1
  7:   0  -120    154   49  -140     70   -14     1
  8:   0   720  -1044 -140   889   -560   154   -20   1
  9:   0 -5040   8028  -64 -6363   4809 -1638   294 -27   1
  10:  0 40320 -69264 8540 50840 -44835 17913 -3990 510 -35  1
  ... reformatted
Recurrence from a- and z-sequence (see above): T(1, 0) = T(0, 0) = 1; T(1, 1) = (1/1)*(1*T(0, 0)) = 1, T(2, 0) = 2*(T(1, 0) - T(1, 1)) = 0, T(2, 1) = (2/1)*(T(1,0) + (-1/2)*T(1, 1)) = 1. T(3, 1) = (3/1)*(0 + (-1/2)*T(2, 1) + (1/6)*T(2, 2)) = -1. (End)
		

Crossrefs

Programs

  • Mathematica
    t[0, 0] = 1; t[n_, k_] := StirlingS1[n, k] + n*StirlingS1[n-1, k]; Table[t[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Dec 04 2013, after Giuliano Cabrele *)

Formula

E.g.f.: (1+y)^(1+x); rows have g.f. k!*binomial(x+1, k); Columns have g.f. (1+x)*log(1+x)^k.
If we define f(n,i,a) = Sum_{k=0..n-i} binomial(n,k)*Stirling1(n-k,i)*Product_{j=0..k-1} (-a-j), then T(n,i) = f(n,i,-1), for n=1,2,...; i=0...n. - Milan Janjic, Dec 21 2008
So T(n,k) = Stirling1(n,k) + n*Stirling1(n-1,k), Stirling1 being the (signed) Stirling numbers of first kind A048994. In terms of lower triangular matrices, 0<= k <= n, T is also the product [Stirling1] * [Pascal] = [A048994] * [A007318], i.e., T(n,k) = Sum_{j=0..n} Stirling1(n,j) * binomial(j,k). - Giuliano Cabrele, Jan 19 2009
This is the triangle of connection constants for expressing the basis of falling factorial polynomials x_(k) := x*(x-1)*...*(x-k+1) in terms of the polynomial sequence (x-1)^n, that is, x_(n) = Sum_{k = 0..n} T(n,k)*(x-1)^k. - Peter Bala, Jul 10 2013
From Wolfdieter Lang, Jun 19 2017: (Start)
Triangle T is the (infinite) matrix product of A048994 (Stirling1) and A007318 (Pascal): T(n,k) = Sum_{m=k..n} Stirling1(n, m)*Pascal(m, k), n >= k >= 0, and 0 for n < k. Note that the Pascal matrix is Sheffer (e^t, t) of the Appell type.
T is the Sheffer (aka exponential Riordan) matrix (1+t, log(1+t)).
E.g.f. column k: (1+x)*(log(1+x))^k/k!, k >= 0.
The a-sequence for T is A027641/A027642 (Bernoulli), and the z-sequence is A033999 (repeat(1,-1)) (see a W. Lang link under A006232 for a- and z-sequences for Sheffer matrices, also for references).
Therefore the combined recurrence is: T(n, 0) = n*Sum_{j=0..n-1} (-1)^j*T(n-1, j), n >= 1, T(0, 0) = 1, and T(n, m) = (n/m)*Sum_{j=0..n-m} binomial(m-1+j, m-1)*Bernoulli(j)*T(n-1, m-1+j), n >= m >= 1. (End)

A269954 Triangle read by rows, T(n,k) = Sum_{j=0..n} C(-j,-n)*S1(j,k), S1 the Stirling cycle numbers A132393, for n>=0 and 0<=k<=n.

Original entry on oeis.org

1, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 2, 5, 3, 1, 0, 9, 20, 17, 6, 1, 0, 44, 109, 100, 45, 10, 1, 0, 265, 689, 694, 355, 100, 15, 1, 0, 1854, 5053, 5453, 3094, 1015, 196, 21, 1, 0, 14833, 42048, 48082, 29596, 10899, 2492, 350, 28, 1
Offset: 0

Views

Author

Peter Luschny, Apr 12 2016

Keywords

Examples

			Triangle starts:
  1;
  0,   1;
  0,   0,   1;
  0,   1,   1,   1;
  0,   2,   5,   3,   1;
  0,   9,  20,  17,   6,   1;
  0,  44, 109, 100,  45,  10,  1;
  0, 265, 689, 694, 355, 100, 15, 1;
		

Crossrefs

A000255 (row sums), A000217 (diag. n,n-1), A133252 (diag. n,n-2).
Columns k=0..4 give A000007, A000166(n-1), A300490(n-1), A381067(n-1), A381068(n-1).

Programs

  • Maple
    A269954 := (n, k) -> add(binomial(-j, -n)*abs(Stirling1(j, k)), j=0..n):
    seq(seq(A269954(n, k), k=0..n), n=0..9);
  • Mathematica
    Flatten[Table[Sum[Binomial[-j,-n] Abs[StirlingS1[j,k]],{j,0,n}], {n,0,9},{k,0,n}]]
  • PARI
    T(n, k) = sum(j=0, n, (-1)^(n-j)*binomial(n-1, n-j)*abs(stirling(j, k)));
    for(n=0, 9, for(k=0, n, print1(T(n, k), ", "))); \\ Seiichi Manyama, Feb 13 2025

A381065 Expansion of e.g.f. -log(1-x)^3 * exp(-x) / 6.

Original entry on oeis.org

0, 0, 0, 1, 2, 15, 85, 609, 4844, 43238, 427090, 4630241, 54683046, 699012093, 9617979007, 141755256889, 2228396376088, 37221746535564, 658390407698084, 12295201090394017, 241749652842156074, 4992277083472634507, 108032799218176059337, 2444797394606939402449
Offset: 0

Views

Author

Seiichi Manyama, Feb 12 2025

Keywords

Crossrefs

Column k=3 of A269953.

Programs

  • PARI
    a(n) = sum(k=0, n, (-1)^(n-k)*binomial(n, k)*abs(stirling(k, 3, 1)));

Formula

a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * |Stirling1(k,3)|.

A381066 Expansion of e.g.f. log(1-x)^4 * exp(-x) / 24.

Original entry on oeis.org

0, 0, 0, 0, 1, 5, 40, 315, 2779, 26817, 282785, 3240325, 40144126, 535152332, 7642713715, 116465389950, 1886911421914, 32395513943998, 587627463812070, 11231176543495238, 225621300685737631, 4753177896741075823, 104793882332694641218, 2413274241933067193021
Offset: 0

Views

Author

Seiichi Manyama, Feb 12 2025

Keywords

Crossrefs

Column k=4 of A269953.

Programs

  • PARI
    a(n) = sum(k=0, n, (-1)^(n-k)*binomial(n, k)*abs(stirling(k, 4, 1)));

Formula

a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * |Stirling1(k,4)|.

A381082 Triangle T(n,k) read by rows, where the columns are the coefficients of the standard expansion of the function f(x) = (-log(1-x))^(k)*exp(-m*x)/k! for the case m=2.

Original entry on oeis.org

1, -2, 1, 4, -3, 1, -8, 8, -3, 1, 16, -18, 11, -2, 1, -32, 44, -20, 15, 0, 1, 64, -80, 94, 5, 25, 3, 1, -128, 272, 56, 294, 105, 49, 7, 1, 256, 112, 1868, 1596, 1169, 392, 98, 12, 1, -512, 5280, 12216, 16148, 10290, 4305, 1092, 186, 18, 1
Offset: 0

Views

Author

Keywords

Examples

			Triangle starts:
  [0]     1;
  [1]    -2,      1;
  [2]     4,     -3,       1;
  [3]    -8,      8,      -3,       1;
  [4]    16,    -18,      11,      -2,       1;
  [5]   -32,     44,     -20,      15,       0,        1;
  [6]    64,    -80,      94,       5,      25,        3,     1;
  [7]  -128,    272,      56,     294,     105,       49,     7,     1;
  [8]   256,    112,    1868,    1596,    1169,      392,    98,    12,    1;
  [9]  -512,   5280,   12216,   16148,   10290,     4305,  1092,   186,   18,     1;
  ...
		

Crossrefs

Cf. A000023 (row sums).
Columns 0,1: A122803, A346397.
Triangles: for m = -3 is A327997; for m = -2 is A137346 (unsigned); for m = -1 is A094816; for m = 0 is A132393; for m = 1 is A269953.

Programs

  • Maple
    T:=(m,n,k)->add(Stirling1(n-i,k)*binomial(n,i)*m^(i)*(-1)^(n-k), i=0..n):
    m:=2:seq(print(seq(T(m,n,k), k=0..n)), n=0..9);

Formula

T(n,k) = Sum_{i=0..n} Stirling1(n-i, k)*binomial(n, i)*m^(i)*(-1)^(n-k), where m = 2.

A381064 Expansion of e.g.f. log(1-x)^2 * exp(-x) / 2.

Original entry on oeis.org

0, 0, 1, 0, 5, 15, 94, 595, 4458, 37590, 354051, 3682646, 41935695, 518954293, 6935360496, 99553094537, 1527716784020, 24959724735564, 432572721886437, 7926615468800172, 153129657663788761, 3110514839038091643, 66278515188844197218, 1478222957082474301887
Offset: 0

Views

Author

Seiichi Manyama, Feb 12 2025

Keywords

Crossrefs

Column k=2 of A269953.

Programs

  • PARI
    a(n) = sum(k=0, n, (-1)^(n-k)*binomial(n, k)*abs(stirling(k, 2, 1)));

Formula

a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(n,k) * |Stirling1(k,2)|.

A002633 Related to discordant permutations.

Original entry on oeis.org

1, -3, 5, -3, 9, -3, -51, -675, -5871, -46467, -331371, -1852227, -920295, 224455293, 5571057501, 104877816093, 1781775072801, 28519837563645, 431525731169061, 5994769814117757, 68879336771960361, 346333945918252797, -15047168730918615315, -793523760950138583843
Offset: 0

Views

Author

Keywords

References

  • 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).

Crossrefs

Programs

  • Mathematica
    a[ n_ ] := a[ n ]=(2n-5)a[ n-1 ]-(n-1)(n-4)a[ n-2 ]-(n-1)(n-2)a[ n-3 ]; a[ 0 ]=1; a[ 1 ]=-3; a[ 2 ]=5; Table[ a[ n ], {n, 0, 24} ] (* Typo fixed by Vaclav Kotesovec, Mar 20 2014 *)

Formula

a(n) - (2n-5)*a(n-1) + (n-1)*(n-4)*a(n-2) + (n-1)*(n-2)*a(n-3) = 0.
From Mélika Tebni, Mar 02 2022: (Start)
a(n) = Sum_{k=0..n} A213170(k)*A269953(n, k).
E.g.f.: exp(-x*(3 - x) / (1 - x)). (End)

Extensions

More terms from Wouter Meeussen
Showing 1-8 of 8 results.