OFFSET
1,1
COMMENTS
The numerator of BernoulliB(12) is 691. The sequence gives semi-indices of the 691-automorphic numerators in the BernoulliB(n) sequence. All 4 initial terms are multiples of 3. Note that Bernoulli numerators corresponding to the first two terms are the automorphic primes: 691 and 1520097643918070802691.
LINKS
Eric Weisstein's World of Mathematics, Bernoulli Number.
EXAMPLE
6 is a term because BernoulliB(2*6) = -691/2730.
21 is a term because BernoulliB(2*21) = 1520097643918070802691/1806.
27 is a term because BernoulliB(2*27) = 29149963634884862421418123812691/798.
MATHEMATICA
Do[ g=Numerator[ BernoulliB[ 2n ] ]; f=Mod[ Abs[ g ], 1000 ]; If[ f==691, Print[ n ] ], {n, 1, 1000}]
Select[Range[10400], Mod[Abs[Numerator[BernoulliB[2#]]], 1000]==691&] (* Harvey P. Dale, May 05 2019 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Alexander Adamchuk, Nov 04 2007
EXTENSIONS
a(5)-a(42) from Donovan Johnson, Sep 05 2008
STATUS
approved