A090648 a(n)=2*(4^n-1)/denominator(B(2n)) where B(k) denotes the k-th Bernoulli number.

0, 1, 1, 3, 17, 31, 3, 5461, 257, 657, 6355, 60787, 12291, 22369621, 617093, 149943, 16843009, 5726623061, 71613, 91625968981, 162529435, 4870483401, 50991843607, 499069107643, 12129927891, 34118178995231, 5664905191661, 45148868444817, 165649641466501

Offset: 0

Author

Benoit Cloitre, Dec 13 2003

Keywords

• nonn

Crossrefs

Cf. A001469.

Programs

Mathematica

Table[(2*(4^n-1))/Denominator[BernoulliB[2n]],{n,0,40}] (* Harvey P. Dale, Jul 20 2011 *)

PARI

a(n)=2*(4^n-1)/denominator(bernfrac(2*n))

Extensions

Corrected and extended by Harvey P. Dale, Jul 20 2011