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A306745

Even bisection of A318256.

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

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OFFSET

0,2

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.

LINKS

Jean-François Alcover, Table of n, a(n) for n = 0..1000

FORMULA

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

MATHEMATICA

sfk[n_] := Times @@ FactorInteger[n][[All, 1]];