A090813 - OEIS

A090813

a(n)=3*(3^prime(n)-1)*B(2*prime(n)) where prime(n)=n-th prime and B(k) denotes the k-th Bernoulli number.

%I #5 Mar 30 2012 18:39:22

%S 55,7651,3290729563,6818200140583,166441513807473717727,

%T 1702709510836284027532747,597359613401618666812910561358019,

%U 49136798858325589887577115786547403314116681479

%N a(n)=3*(3^prime(n)-1)*B(2*prime(n)) where prime(n)=n-th prime and B(k) denotes the k-th Bernoulli number.

%C Appears to be an integer value for n=3 up to 250.

%o (PARI) a(n)=3*(3^prime(n)-1)*bernfrac(2*prime(n))

%K nonn

%O 3,1

%A _Benoit Cloitre_, Feb 11 2004