0,4

A001897 give the denominators of |Bernoulli(n)*Gould(n)| for even n, also the denominators of the cosecant numbers.

b := n -> bernoulli(n)*2^add(i, i=convert(n, base, 2));

a := n -> numer(abs(b(2*n)));

Cf. A001897

Sequence in context: A133103 A054781 A098290 this_sequence A139393 A037916 A143888

Adjacent sequences: A160107 A160108 A160109 this_sequence A160111 A160112 A160113

frac,nonn

Peter Luschny (peter(AT)luschny.de), May 02 2009