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.

A306745 Even bisection of A318256.

Original entry on oeis.org

1, 2, 6, 6, 10, 6, 210, 2, 30, 210, 110, 30, 546, 14, 30, 462, 1190, 6, 51870, 70, 2310, 2310, 322, 210, 6630, 286, 330, 798, 290, 30, 930930, 1430, 1122, 82110, 70, 330, 21111090, 38038, 390, 210, 536690, 39270, 7489482, 10010, 62790, 4470510, 687610, 462
Offset: 0

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Comments

The ratio sequence of a(n)/A006955(n) begins: 1,1,1,1,1,1,1,1,1,5,1,5,1,7,1,1,7,1,1,35, ...
This divisibility by A006955 was confirmed by Peter Luschny in the SeqFan mailing list.

Crossrefs

Programs

  • Mathematica
    sfk[n_] := Times @@ FactorInteger[n][[All, 1]];
    a[n_] := (BernoulliB[2 n, x] // Together // Denominator)/sfk[2 n + 1];
    Table[a[n], {n, 0, 60}]

Formula

a(n) = (denominator of B(2n,x)) / (the squarefree kernel of 2n+1), where B(2n,x) is the 2n-th Bernoulli polynomial.