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 1-3 of 3 results.

A291261 Square array A(n,k), n >= 0, k >= 0, read by antidiagonals, where column k is the expansion of continued fraction 1/(1 - x/(1 - 3^k*x/(1 - 5^k*x/(1 - 7^k*x/(1 - 9^k*x/(1 - ...)))))).

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 1, 1, 4, 5, 1, 1, 10, 31, 14, 1, 1, 28, 325, 364, 42, 1, 1, 82, 4159, 22150, 5746, 132, 1, 1, 244, 57349, 1790452, 2586250, 113944, 429, 1, 1, 730, 818911, 162045118, 1691509906, 461242900, 2719291, 1430, 1, 1, 2188, 11923525, 15520964284, 1289803048426, 2978600051368, 116651486125, 75843724, 4862
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 21 2017

Keywords

Examples

			Square array begins:
   1,     1,        1,           1,              1,                 1,  ...
   1,     1,        1,           1,              1,                 1,  ...
   2,     4,       10,          28,             82,               244,  ...
   5,    31,      325,        4159,          57349,            818911,  ...
  14,   364,    22150,     1790452,      162045118,       15520964284,  ...
  42,  5746,  2586250,  1691509906,  1289803048426,  1063421637466546,  ...
		

Crossrefs

Columns k=0..2 give A000108, A128709, A127823.
Main diagonal gives A291332.
Cf. A034472 (row 2), A290569, A291260.

Programs

  • Mathematica
    Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-(2 i - 1)^k x, 1, {i, 1, n}]), {x, 0, n}]][j - n], {j, 0, 9}, {n, 0, j}] // Flatten

Formula

G.f. of column k: 1/(1 - x/(1 - 3^k*x/(1 - 5^k*x/(1 - 7^k*x/(1 - 9^k*x/(1 - ...)))))), a continued fraction.

A291547 a(n) = ((2*n-1)!!)^n.

Original entry on oeis.org

1, 9, 3375, 121550625, 753631499840625, 1261673443947253805015625, 822952789790387281855874669859609375, 285018362247755338974104595257347347998199462890625, 68512882179510153729154120317673085873841328059500855014801025390625
Offset: 1

Views

Author

Vaclav Kotesovec, Aug 26 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Product[2*k - 1, {k, 1, n}]^n, {n, 1, 10}]
    Table[((2*n - 1)!!)^n, {n, 1, 10}]

Formula

a(n) = ((2*n)!/n!)^n / 2^(n^2).
a(n) ~ 2^(n^2 + n/2) * n^(n^2) / exp(n^2 + 1/24).

A317103 Expansion of e.g.f. -LambertW(-x) * Product_{k>=1} 1/(1-x^k).

Original entry on oeis.org

0, 1, 4, 27, 220, 2265, 27246, 393421, 6548536, 126257697, 2767122010, 68387691141, 1882488882660, 57198150690577, 1900138953826582, 68502961685976525, 2662089147552365296, 110887849449189768513, 4926985461324765096498, 232544882903837769171829
Offset: 0

Views

Author

Vaclav Kotesovec, Jul 21 2018

Keywords

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[-LambertW[-x]*Product[1/(1-x^k), {k, 1, nmax}], {x, 0, nmax}], x] * Range[0, nmax]!
    Table[n!*Sum[PartitionsP[n-k]*k^(k-1)/k!, {k, 1, n}], {n, 0, 20}]

Formula

a(n) ~ c * n^(n-1), where c = 1/QPochhammer(exp(-1)) = 1.98244090741287370368568246556131... - Vaclav Kotesovec, Jul 21 2018
Showing 1-3 of 3 results.