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.

A362856 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{j=0..n} (-k)^(n-j) * j^j * binomial(n,j).

Original entry on oeis.org

1, 1, 1, 1, 0, 4, 1, -1, 3, 27, 1, -2, 4, 17, 256, 1, -3, 7, 7, 169, 3125, 1, -4, 12, -9, 120, 2079, 46656, 1, -5, 19, -37, 121, 1373, 31261, 823543, 1, -6, 28, -83, 208, 797, 21028, 554483, 16777216, 1, -7, 39, -153, 441, 21, 14517, 373931, 11336753, 387420489
Offset: 0

Views

Author

Seiichi Manyama, May 05 2023

Keywords

Examples

			Square array begins:
     1,    1,    1,   1,   1,     1, ...
     1,    0,   -1,  -2,  -3,    -4, ...
     4,    3,    4,   7,  12,    19, ...
    27,   17,    7,  -9, -37,   -83, ...
   256,  169,  120, 121, 208,   441, ...
  3125, 2079, 1373, 797,  21, -1525, ...
		

Crossrefs

Columns k=0..3 give A000312, (-1)^n * A069856(n), A362857, A362858.
Main diagonal gives A290158.
Cf. A362019.

Programs

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

Formula

E.g.f. of column k: exp(-k*x) / (1 + LambertW(-x)).
G.f. of column k: Sum_{j>=0} (j*x)^j / (1 + k*x)^(j+1).

A362836 Expansion of e.g.f. 1/(1 + LambertW(-x * (exp(x) - 1))).

Original entry on oeis.org

1, 0, 2, 3, 52, 245, 4086, 36547, 663832, 8984313, 184262770, 3334315391, 77900601780, 1751855308645, 46508427942718, 1241853335819475, 37195023972070576, 1144511291020453361, 38337497638919397738, 1331709923436162817447
Offset: 0

Views

Author

Seiichi Manyama, May 05 2023

Keywords

Crossrefs

Programs

  • PARI
    my(N=20, x='x+O('x^N)); Vec(serlaplace(1/(1+lambertw(-x*(exp(x)-1)))))

Formula

a(n) = n! * Sum_{k=0..floor(n/2)} k^k * Stirling2(n-k,k)/(n-k)!.
a(n) ~ n^n / (sqrt(exp(r)*(1+r) - 1) * r^(n + 1/2) * exp(n + 1/2)), where r = 0.528399250336668412340528181936966763473... is the root of the equation exp(1+r)-exp(1) = 1/r. - Vaclav Kotesovec, May 19 2025

A361652 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = n! * Sum_{j=0..floor(n/2)} k^j * Stirling2(n-j,j)/(n-j)!.

Original entry on oeis.org

1, 1, 0, 1, 0, 0, 1, 0, 2, 0, 1, 0, 4, 3, 0, 1, 0, 6, 6, 16, 0, 1, 0, 8, 9, 56, 65, 0, 1, 0, 10, 12, 120, 250, 336, 0, 1, 0, 12, 15, 208, 555, 1812, 1897, 0, 1, 0, 14, 18, 320, 980, 5148, 12614, 11824, 0, 1, 0, 16, 21, 456, 1525, 11064, 39711, 101040, 80145, 0
Offset: 0

Views

Author

Seiichi Manyama, May 05 2023

Keywords

Examples

			Square array begins:
  1,  1,   1,   1,   1,    1, ...
  0,  0,   0,   0,   0,    0, ...
  0,  2,   4,   6,   8,   10, ...
  0,  3,   6,   9,  12,   15, ...
  0, 16,  56, 120, 208,  320, ...
  0, 65, 250, 555, 980, 1525, ...
		

Crossrefs

Columns k=0..3 give: A000007, A052506, A351733, A351734.
Main diagonal gives (-1)^n * A290158(n).
Cf. A362834.

Programs

  • PARI
    T(n, k) = n!*sum(j=0, n\2, k^j*stirling(n-j, j, 2)/(n-j)!);

Formula

E.g.f. of column k: exp(k * x * (exp(x) - 1)).

A362862 a(n) = (-1)^n * Sum_{k=0..n} (-n*k)^k * binomial(n,k).

Original entry on oeis.org

1, 0, 13, 629, 58993, 8998399, 2035844461, 640881617123, 267995012680641, 143734541641235567, 96200314049944377901, 78599287990433271805699, 76993408916168689318057201, 89072357257840197226050646151
Offset: 0

Views

Author

Seiichi Manyama, May 06 2023

Keywords

Crossrefs

Main diagonal of A362019.
Cf. A290158.

Programs

  • Mathematica
    Table[(-1)^n*(1 + Sum[(-n*k)^k*Binomial[n, k], {k, 1, n}]), {n, 0, 20}] (* Vaclav Kotesovec, Aug 07 2025 *)
  • PARI
    a(n) = (-1)^n * sum(k=0, n, (-n*k)^k*binomial(n, k));

Formula

a(n) = n! * [x^n] exp(-x) / (1 + LambertW(-n*x)).
a(n) = [x^n] Sum_{k>=0} (n*k*x)^k / (1 + x)^(k+1).
Showing 1-4 of 4 results.