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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A291652 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of k-th power of continued fraction 1/(1 - x/(1 - x^2/(1 - x^3/(1 - x^4/(1 - x^5/(1 - ...)))))).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 1, 0, 1, 3, 3, 2, 0, 1, 4, 6, 6, 3, 0, 1, 5, 10, 13, 11, 5, 0, 1, 6, 15, 24, 27, 20, 9, 0, 1, 7, 21, 40, 55, 54, 38, 15, 0, 1, 8, 28, 62, 100, 120, 109, 70, 26, 0, 1, 9, 36, 91, 168, 236, 258, 216, 129, 45, 0, 1, 10, 45, 128, 266, 426, 540, 544, 423, 238, 78, 0, 1, 11, 55, 174, 402, 721, 1035, 1205, 1127, 824, 437, 135, 0
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 28 2017

Keywords

Examples

			G.f. of column k: A_k(x) = 1 + k*x + k*(k + 1)*x^2/2 +  k*(k^2 + 3*k + 8)*x^3/6 + k*(k^3 + 6*k^2 + 35*k + 30)*x^4/24 + ...
Square array begins:
1,  1,   1,   1,    1,    1,  ...
0,  1,   2,   3,    4,    5,  ...
0,  1,   3,   6,   10,   15,  ...
0,  2,   6,  13,   24,   40,  ...
0,  3,  11,  27,   55,  100,  ...
0,  5,  20,  54,  120,  236,  ...
		

Crossrefs

Columns k=0..1 give A000007, A005169.
Rows n=0..3 give A000012, A001477, A000217, A003600 (with a(0)=0).
Main diagonal gives A291653.

Programs

  • Mathematica
    Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-x^i, 1, {i, 1, n}])^k, {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten
    Table[Function[k, SeriesCoefficient[((Sum[(-1)^i x^(i (i + 1))/Product[(1 - x^m), {m, 1, i}], {i, 0, n}])/(Sum[(-1)^i x^(i^2)/Product[(1 - x^m), {m, 1, i}], {i, 0, n}]))^k, {x, 0, n}]][j - n], {j, 0, 12}, {n, 0, j}] // Flatten

Formula

G.f. of column k: (1/(1 - x/(1 - x^2/(1 - x^3/(1 - x^4/(1 - x^5/(1 - ...)))))))^k, a continued fraction.

A291274 a(n) = [x^n] 1/(1 - n*x/(1 - n*x^2/(1 - n*x^3/(1 - n*x^4/(1 - n*x^5/(1 - ...)))))), a continued fraction.

Original entry on oeis.org

1, 1, 4, 36, 384, 5125, 81864, 1519833, 32219136, 768352149, 20367510000, 594270942705, 18929706034176, 653744865197242, 24333393186194848, 971177936039212500, 41376191798281502720, 1874320475909920820607, 89961819584112859211712, 4560744533588836253021837
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 22 2017

Keywords

Crossrefs

Main diagonal of A286933.

Programs

  • Mathematica
    Table[SeriesCoefficient[1/(1 + ContinuedFractionK[-n x^i, 1, {i, 1, n}]), {x, 0, n}], {n, 0, 19}]

Formula

a(n) = A286933(n,n).
a(n) ~ exp(1) * n^n. - Vaclav Kotesovec, Aug 26 2017
Showing 1-2 of 2 results.