A090629 - OEIS

A090629

a(n) = abs(numerator of 2n-th Bernoulli number) modulo 3.

1, 1, 1, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 2, 2, 2, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 2, 2, 1, 2, 1, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 2, 2, 1, 2, 2, 1, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 1, 1, 1, 2, 1, 1, 2, 2, 1, 1, 1, 1

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OFFSET

0,6

LINKS

Table of n, a(n) for n=0..104.

FORMULA

a(n) = abs(A000367(n)) (mod 3)

MATHEMATICA

Mod[Abs[Numerator[BernoulliB[2*Range[0, 120]]]], 3] (* Harvey P. Dale, Nov 16 2021 *)

PROG

(PARI) a(n)=abs(numerator(bernfrac(2*n)))%3

CROSSREFS