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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A286509 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, 0, 0, 1, -4, 6, -2, -1, 0, 1, -5, 10, -7, -1, 1, 0, 1, -6, 15, -16, 3, 4, -1, 0, 1, -7, 21, -30, 15, 6, -6, 1, 0, 1, -8, 28, -50, 40, 0, -17, 6, 0, 0, 1, -9, 36, -77, 84, -26, -30, 24, -3, -1, 0, 1, -10, 45, -112, 154, -90, -30, 64, -21, -2, 2, 0, 1, -11, 55, -156, 258, -217, 15, 125, -81, 6, 9, -3, 0
Offset: 0

Views

Author

Ilya Gutkovskiy, May 10 2017

Keywords

Examples

			Square array begins:
1,  1,  1,  1,   1,   1,  ...
0, -1, -2, -3,  -4,  -5,  ...
0,  1,  3,  6,  10,  15,  ...
0,  0, -2, -7, -16, -30,  ...
0, -1, -1,  3,  15,  40,  ...
0,  1,  4,  6,   0, -26,  ...
		

Crossrefs

Columns k=0-5 give: A000007, A007325, A055101, A055102, A055103, A078905 (with offset 0).
Rows n=0-2 give: A000012, A001489, A000217.
Main diagonal gives A291651.
Antidiagonal sums give A302015.

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[Product[(1 - x^(5 i - 1)) (1 - x^(5 i - 4))/((1 - x^(5 i - 2)) (1 - x^(5 i - 3))), {i, n}]^k, {x, 0, n}]][j - n], {j, 0, 12},{n, 0, j}] // Flatten

Formula

G.f. of column k: Product_{j>=1} ((1 - x^(5*j-1))*(1 - x^(5*j-4)) / ((1 - x^(5*j-2))*(1 - x^(5*j-3))))^k.

A302016 Expansion of 1/(1 - x - x^2/(1 + x^2/(1 + x^3/(1 + x^4/(1 + x^5/(1 + ...)))))), a continued fraction.

Original entry on oeis.org

1, 1, 2, 3, 4, 6, 9, 14, 21, 31, 46, 68, 102, 153, 229, 342, 510, 761, 1136, 1697, 2535, 3786, 5653, 8441, 12605, 18824, 28112, 41981, 62691, 93617, 139800, 208768, 311761, 465564, 695242, 1038226, 1550415, 2315284, 3457489, 5163181, 7710344, 11514102, 17194374, 25676907, 38344147
Offset: 0

Views

Author

Ilya Gutkovskiy, Mar 30 2018

Keywords

Crossrefs

Antidiagonal sums of A291678.

Programs

  • Mathematica
    nmax = 44; CoefficientList[Series[1/(1 - x - x^2/(1 + ContinuedFractionK[x^k, 1, {k, 2, nmax}])), {x, 0, nmax}], x]
    nmax = 44; CoefficientList[Series[1/(1 - x QPochhammer[x^2, x^5] QPochhammer[x^3, x^5]/(QPochhammer[x, x^5] QPochhammer[x^4, x^5])), {x, 0, nmax}], x]

Formula

G.f.: 1/(1 - x*Product_{k>=1} (1 - x^(5*k-2))*(1 - x^(5*k-3))/((1 - x^(5*k-1))*(1 - x^(5*k-4)))).
a(0) = 1; a(n) = Sum_{k=1..n} A003823(k-1)*a(n-k).
a(n) ~ c / r^n, where r = 0.669643458685499460127124120930664114507093547265881... is the root of the equation x*QPochhammer[x^2, x^5]*QPochhammer[x^3, x^5] = QPochhammer[x, x^5]*QPochhammer[x^4, x^5] and c = 0.833333547701931811823757549354805979633827853516233646128015838266... - Vaclav Kotesovec, Jun 08 2019
Showing 1-2 of 2 results.