A090818 - OEIS

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A090818

Nonprimes n such that 3*(3^n-1)*B(2n) is an integer, where B(k) denotes the k-th Bernoulli number.

0

1, 4, 12, 16, 25, 28, 32, 35, 36, 48, 49, 52, 55, 64, 65, 76, 77, 80, 84, 85, 91, 92, 95, 96, 108, 112, 115, 119, 121, 124, 125, 133, 143, 144, 145, 148, 155, 156, 160, 161, 164, 169, 172, 175, 185, 187, 188, 192, 196, 203, 205, 208, 209, 212, 215, 217, 221, 228

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OFFSET

1,2

COMMENTS

It appears that a(n) is never == 2 (mod 4)

LINKS

Table of n, a(n) for n=1..58.

PROG

(PARI) a(n)=denominator(bernfrac(2*prime(n)))

CROSSREFS

Sequence in context: A186303 A073687 A187084 * A075191 A320922 A028594

Adjacent sequences: A090815 A090816 A090817 * A090819 A090820 A090821

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Feb 11 2004

STATUS

approved