A090814 a(n)=3*(3^prime(n)-1)/denominator(B(2*prime(n))) where prime(n)=n-th prime and B(k) denotes the k-th Bernoulli number.

11, 1093, 3851, 797161, 64570081, 581130733, 1001523179, 581613367499, 308836698141973, 225141952945498681, 219716845645607147, 164128483697268538813, 13294407179478751643893, 90575914334953364003723

Offset: 3

Author

Benoit Cloitre, Feb 11 2004

Keywords

• nonn

Comments

Appears to be an integer for n from 3 up to 250.

Programs

Mathematica

pB[n_]:=Module[{p=Prime[n]},3 (3^p-1)/Denominator[BernoulliB[2p]]]; Array[ pB,20,3] (* Harvey P. Dale, Apr 20 2019 *)

PARI

a(n)=3*(3^prime(n)-1)/denominator(bernfrac(2*prime(n)))