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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A255811 Rectangular array: row n gives the numerators in the positive convolutory n-th root of (1,1,1,...).

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 5, 2, 1, 1, 1, 35, 14, 5, 1, 1, 1, 63, 35, 15, 3, 1, 1, 1, 231, 91, 195, 11, 7, 1, 1, 1, 429, 728, 663, 44, 91, 4, 1, 1, 1, 6435, 1976, 4641, 924, 1729, 20, 9, 1, 1, 1, 12155, 5434, 16575, 4004, 8645, 110, 51, 5, 1, 1, 1
Offset: 1

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Author

Clark Kimberling, Mar 11 2015

Keywords

Comments

The convolution n times of the sequence comprising row n is the constant sequence (1,1,1,...) = A000012.
It appears that if n+1 is a prime (A000040), then most of the terms in row n are divisible by n+1. Taking n = 4 for an example, 968 of the first 1000 terms are divisible by 5.
Is (column 4) = A175485, the numerators of averages of squares of 1,...,n?

Examples

			First, regarding the numbers numerator/denominator, we have
row 1:  1,1,1,1,1,1,1,1,1,1,1,1,1,..., the 0th self-convolution of (1,1,1,...);
row 2:  1,1/2,3/8,5/16,35/128,63/256, ..., convolutory sqrt of (1,1,1,...);
row 3:  1,1/3,2/9,14/81,35/243,91/729,..., convolutory 3rd root;
row 4:  1,1/4,5/32,15/128,195/2048,663/8192,..., convolutoary 4th root.
Taking only numerators:
row 1:  1,1,1,1,1,1,1,...
row 2:  1,1,3,5,35,63,...
row 3:  1,1,2,14,35,91,...
row 4:  1,1,5,15,195,663,...
		

Crossrefs

Programs

  • Mathematica
    z = 15; t[n_] := CoefficientList[Normal[Series[(1 - t)^(-1/n), {t, 0, z}]], t];
    u = Table[Numerator[t[n]], {n, 1, z}]
    TableForm[Table[u[[n, k]], {n, 1, z}, {k, 1, z}]]     (* A255811 array *)
    Table[u[[n - k + 1, k]], {n, z}, {k, n, 1, -1}] // Flatten (* A255811 sequence *)
    v = Table[Denominator[t[n]], {n, 1, z}]
    TableForm[Table[v[[n, k]], {n, 1, z}, {k, 1, z}]]     (* A255812 array *)
    Table[v[[n - k + 1, k]], {n, z}, {k, n, 1, -1}] // Flatten  (* A255812 sequence *)

Formula

G.f. of s: (1 - t)^(-1/n).
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