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.

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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.

A291331 a(n) = [x^n] 1/(1 - 2^n*x/(1 - 4^n*x/(1 - 6^n*x/(1 - 8^n*x/(1 - 10^n*x/(1 - ...)))))), a continued fraction.

Original entry on oeis.org

1, 2, 80, 152064, 31832735744, 1278532180456243200, 15158097871912903189326725120, 75553979800594222861911290918096439607296, 213679399657239557797941463213636090471439135194537263104
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 22 2017

Keywords

Crossrefs

Main diagonal of A291260.
Cf. A291333.

Programs

  • Mathematica
    Table[SeriesCoefficient[1/(1 + ContinuedFractionK[-(2 i)^n x, 1, {i, 1, n}]), {x, 0, n}], {n, 0, 8}]

Formula

a(n) = A291260(n,n).
a(n) ~ c * 2^(n^2) * (n!)^n ~ c * Pi^(n/2) * (2*n)^(n^2 + n/2) / exp(n^2 - 1/12), where c = 1/QPochhammer(exp(-1)) = 1.982440907412873703685682465561312... - Vaclav Kotesovec, Jun 08 2019
Showing 1-2 of 2 results.