A079294 - OEIS

A079294

Number of distinct prime factors of the numerator of the 2n-th Bernoulli number.

0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 2, 2, 3, 3, 3, 2, 1, 2, 2, 1, 5, 3, 3, 3, 5, 3, 4, 5, 3, 5, 2, 3, 6, 5, 2, 2, 3, 4, 5, 4, 5, 4, 4, 4, 4, 6, 5, 6, 5, 7, 5, 5, 3, 6, 4, 2, 5, 2, 3, 4, 9, 4, 6, 7, 4, 5, 4, 8, 8, 4, 2, 7, 7, 7, 7, 8, 5, 8, 6, 5, 8, 9, 6, 5, 3, 8

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OFFSET

0,11

LINKS

Amiram Eldar, Table of n, a(n) for n = 0..103

S. S. Wagstaff, Jr., Factors of Bernoulli numbers

FORMULA

a(n) = A001221(abs(A000367(n))). - Amiram Eldar, Feb 09 2020

MATHEMATICA

Table[PrimeNu[Numerator[BernoulliB[2n]]], {n, 0, 30}] (* Amiram Eldar, Feb 09 2020 *)

PROG

(PARI) a(n)=omega(numerator(bernfrac(2*n)))