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.

A351761 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = n! * Sum_{j=0..n} k^(n-j) * (n-j)^j/j!.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 4, 0, 1, 3, 12, 21, 0, 1, 4, 24, 102, 148, 0, 1, 5, 40, 279, 1160, 1305, 0, 1, 6, 60, 588, 4332, 16490, 13806, 0, 1, 7, 84, 1065, 11536, 84075, 281292, 170401, 0, 1, 8, 112, 1746, 25220, 282900, 1958058, 5598110, 2403640, 0
Offset: 0

Views

Author

Seiichi Manyama, Feb 18 2022

Keywords

Examples

			Square array begins:
  1,    1,     1,     1,      1,      1, ...
  0,    1,     2,     3,      4,      5, ...
  0,    4,    12,    24,     40,     60, ...
  0,   21,   102,   279,    588,   1065, ...
  0,  148,  1160,  4332,  11536,  25220, ...
  0, 1305, 16490, 84075, 282900, 746525, ...
		

Crossrefs

Columns k=0..3 give A000007, A006153, A351762, A351763.
Main diagonal gives A351765.

Programs

  • PARI
    T(n, k) = n!*sum(j=0, n, k^(n-j)*(n-j)^j/j!);
    
  • PARI
    T(n, k) = if(n==0, 1, k*n*sum(j=0, n-1, binomial(n-1, j)*T(j, k)));

Formula

E.g.f. of column k: 1/(1 - k*x*exp(x)).
T(0,k) = 1 and T(n,k) = k * n * Sum_{j=0..n-1} binomial(n-1,j) * T(j,k) for n > 0.

A351768 a(n) = n! * Sum_{k=0..n} k^(n-k) * (n-k)^k/k!.

Original entry on oeis.org

1, 0, 2, 18, 276, 6260, 190950, 7523082, 371286440, 22356290952, 1608686057610, 136069954606190, 13345029902628732, 1500054487474871484, 191349476316804534638, 27464505325501082617170, 4402551348139824475260240, 783025812197886669354545552
Offset: 0

Views

Author

Seiichi Manyama, Feb 18 2022

Keywords

Crossrefs

Programs

  • Mathematica
    Join[{1}, Table[n!*Sum[k^(n-k) * (n-k)^k/k!, {k, 0, n}], {n, 1, 20}]] (* Vaclav Kotesovec, Feb 19 2022 *)
  • PARI
    a(n) = n!*sum(k=0, n, k^(n-k)*(n-k)^k/k!);

Formula

log(a(n)) ~ n *(2*log(n) - log(log(n)) - 2 + (log(log(n)) + log(log(n)-1) + 1)/log(n)). - Vaclav Kotesovec, Feb 19 2022

A351779 a(n) = n! * Sum_{k=0..n} (-n)^(n-k) * (n-k)^k/k!.

Original entry on oeis.org

1, -1, 4, -63, 2288, -138525, 12381084, -1528482823, 249005711296, -51739455340953, 13353206066063900, -4190486732316600771, 1571373340568392914288, -693899460077821703051125, 356404409990391961980227068, -210670220153918100996704166975
Offset: 0

Views

Author

Seiichi Manyama, Feb 19 2022

Keywords

Crossrefs

Main diagonal of A351776.

Programs

  • PARI
    a(n) = n!*sum(k=0, n, (-n)^(n-k)*(n-k)^k/k!);

Formula

a(n) = n! * [x^n] 1/(1 + n*x*exp(x)).

A295623 a(n) = n! * [x^n] exp(n*x*exp(x)).

Original entry on oeis.org

1, 1, 8, 90, 1424, 28900, 716292, 20972098, 708317248, 27108056808, 1159375192100, 54799938951934, 2836735081572240, 159606310760007436, 9698172715195196260, 632924646574215596850, 44153807025286701187328, 3278903858941755472870864, 258247909552273997037934788
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 24 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[n! SeriesCoefficient[Exp[n x Exp[x]], {x, 0, n}], {n, 0, 18}]
    Table[Sum[BellY[n, k, n Range[n]], {k, 0, n}], {n, 0, 18}]
  • PARI
    a(n) = sum(k=0, n, n^k*k^(n-k)*binomial(n, k)); \\ Seiichi Manyama, Jul 04 2022

Formula

a(n) = n! * [x^n] exp(n*Sum_{k>=1} x^k/(k - 1)!).
From Seiichi Manyama, Jul 05 2022: (Start)
a(n) = [x^n] Sum_{k>=0} (n * x)^k/(1 - k*x)^(k+1).
a(n) = Sum_{k=0..n} n^k * k^(n-k) * binomial(n,k). (End)
Showing 1-4 of 4 results.