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 1-4 of 4 results.

A330603 a(n) = Sum_{k>=0} (k - n)^n / 2^(k + 1).

Original entry on oeis.org

1, 0, 3, -14, 155, -1834, 27867, -492246, 10068459, -232990178, 6025718963, -172182404734, 5387697769467, -183214963001082, 6728091949444491, -265348057242998822, 11185888456798395563, -501937946696294628946, 23886968118494957119011, -1201674025637823778926414
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 19 2019

Keywords

Comments

The n-th term of the n-th inverse binomial transform of A000670.

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 50);
    A330603:= func< n | Coefficient(R!(Laplace( Exp(-n*x)/(2-Exp(x)) )), n) >;
    [A330603(n): n in [0..30]]; // G. C. Greubel, Jun 12 2024
    
  • Mathematica
    Table[Sum[(k - n)^n/2^(k + 1), {k, 0, Infinity}], {n, 0, 19}]
    Table[HurwitzLerchPhi[1/2, -n, -n]/2, {n, 0, 19}]
    Table[n! SeriesCoefficient[Exp[-n x]/(2 - Exp[x]), {x, 0, n}], {n, 0, 19}]
  • SageMath
    [factorial(n)*( exp(-n*x)/(2-exp(x)) ).series(x,n+1).list()[n] for n in (0..30)] # G. C. Greubel, Jun 12 2024

Formula

a(n) = n! * [x^n] exp(-n*x) / (2 - exp(x)).
a(n) = Sum_{k=0..n} binomial(n,k) * (-n)^(n - k) * A000670(k).
a(n) ~ (-1)^n * n^n / (2 - exp(-1)). - Vaclav Kotesovec, Dec 19 2019

A292915 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of e.g.f. exp(k*x)/(2 - exp(x)).

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 1, 3, 6, 13, 1, 4, 11, 26, 75, 1, 5, 18, 51, 150, 541, 1, 6, 27, 94, 299, 1082, 4683, 1, 7, 38, 161, 582, 2163, 9366, 47293, 1, 8, 51, 258, 1083, 4294, 18731, 94586, 545835, 1, 9, 66, 391, 1910, 8345, 37398, 189171, 1091670, 7087261, 1, 10, 83, 566, 3195, 15666, 74067, 378214, 2183339, 14174522, 102247563
Offset: 0

Views

Author

Ilya Gutkovskiy, Sep 26 2017

Keywords

Comments

A(n,k) is the k-th binomial transform of A000670 evaluated at n.

Examples

			E.g.f. of column k: A_k(x) = 1 + (k + 1)*x/1! + (k^2 + 2*k + 3)*x^2/2! + (k^3 + 3*k^2 + 9*k + 13)*x^3/3! +  (k^4 + 4*k^3 + 18*k^2 + 52*k + 75) x^4/4! + ...
Square array begins:
    1,     1,     1,     1,     1,      1,  ...
    1,     2,     3,     4,     5,      6,  ...
    3,     6,    11,    18,    27,     38,  ...
   13,    26,    51,    94,   161,    258,  ...
   75,   150,   299,   582,  1083,   1910,  ...
  541,  1082,  2163,  4294,  8345,  15666,  ...
		

Crossrefs

Columns k=0..4 give A000670, A000629, A007047, A259533, A368317.
Rows n=0..2 give A000012, A000027, A102305.
Main diagonal gives A292916.

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 50);
    T:= func< n,k | Coefficient(R!(Laplace( Exp(k*x)/(2-Exp(x)) )), n) >;
    A292915:= func< n,k | T(k,n-k) >;
    [A292915(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Jun 12 2024
    
  • Maple
    A:= proc(n, k) option remember; k^n +add(
           binomial(n, j)*A(j, k), j=0..n-1)
        end:
    seq(seq(A(n, d-n), n=0..d), d=0..12);  # Alois P. Heinz, Sep 27 2017
  • Mathematica
    Table[Function[k, n! SeriesCoefficient[Exp[k x]/(2 - Exp[x]), {x, 0, n}]][j - n], {j, 0, 10}, {n, 0, j}] // Flatten
    Table[Function[k, HurwitzLerchPhi[1/2, -n, k]/2][j - n], {j, 0, 10}, {n, 0, j}] // Flatten
  • PARI
    a000670(n) = sum(k=0, n, k!*stirling(n, k, 2));
    A(n, k) = 2^k*a000670(n)-sum(j=0, k-1, 2^j*(k-1-j)^n); \\ Seiichi Manyama, Dec 25 2023
    
  • SageMath
    def T(n,k): return factorial(n)*( exp(k*x)/(2-exp(x)) ).series(x, n+1).list()[n]
    def A292915(n,k): return T(k,n-k)
    flatten([[A292915(n,k) for k in range(n+1)] for n in range(13)]) # G. C. Greubel, Jun 12 2024

Formula

E.g.f. of column k: exp(k*x)/(2 - exp(x)).
A(n,k) = 2^k*A000670(n) - Sum_{j=0..k-1} 2^j*(k-1-j)^n. - Seiichi Manyama, Dec 25 2023

A337027 a(n) = (1/2) * Sum_{k>=0} (2*k + n)^n / 2^k.

Original entry on oeis.org

1, 3, 24, 293, 4784, 97687, 2393472, 68405073, 2233928448, 82063263371, 3349249267712, 150353137462717, 7362889615257600, 390601858379350815, 22315011551291080704, 1365896953310909493929, 89179296762081886011392, 6186383336743041502051219
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 11 2020

Keywords

Crossrefs

Programs

  • Mathematica
    Table[2^(n - 1) HurwitzLerchPhi[1/2, -n, n/2], {n, 0, 17}]
    Table[n! SeriesCoefficient[Exp[n x]/(2 - Exp[2 x]), {x, 0, n}], {n, 0, 17}]

Formula

a(n) = n! * [x^n] exp(n*x) / (2 - exp(2*x)).
a(n) = Sum_{k=0..n} binomial(n,k) * n^k * A216794(n-k).

A340838 a(n) = (1/2) * Sum_{k>=0} (k*(k + n))^n / 2^k.

Original entry on oeis.org

1, 4, 139, 11928, 1909787, 491329088, 185373016419, 96425597012608, 66139668570414571, 57840395870803141632, 62813828698519808489915, 82933938539372018962724864, 130828514220436815006398809563, 243020960809424084526916839817216, 525038425527430196237626528753654867
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 23 2021

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(1/2) Sum[(k (k + n))^n/2^k, {k, 0, Infinity}], {n, 0, 14}]
    Join[{1}, Table[(1/2) Sum[Binomial[n, k] HurwitzLerchPhi[1/2, k - 2 n, 0] n^k, {k, 0, n}], {n, 1, 14}]]

Formula

a(n) = Sum_{k=0..n} binomial(n,k) * A000670(2*n-k) * n^k.
Showing 1-4 of 4 results.