A084217 - OEIS

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A084217

Number of k's 1<=k<=n dividing the numerator of 2n-th Bernoulli number.

1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 1, 1, 2, 2, 1, 3, 2, 1, 2, 2, 1, 2, 1, 2, 2, 4, 1, 2, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 1, 3, 1, 2, 3, 2, 1, 2, 2, 2, 2, 2, 1, 2, 2, 1, 1, 4, 2, 2, 2, 2, 3, 2, 1, 2, 2, 3, 2, 4, 1, 2, 2, 1, 2, 2, 1, 4, 2, 2, 3, 2, 1, 4, 2, 2, 2, 5, 1, 2, 3, 2, 1, 2, 2, 2, 2, 2

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OFFSET

1,5

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..5530

Wikipedia, Bernoulli numbers

PROG

(PARI) a(n)=sum(k=1, n, if(numerator(bernfrac(2*n))%k, 0, 1))

CROSSREFS

Cf. A000367.

Sequence in context: A227945 A003647 A353352 * A245548 A025903 A175327

Adjacent sequences: A084214 A084215 A084216 * A084218 A084219 A084220