A165949 a(n) = A027762(n)/A165734(n).

1, 1, 7, 1, 11, 91, 1, 17, 133, 11, 23, 91, 1, 29, 2387, 17, 1, 63973, 1, 451, 301, 23, 47, 1547, 11, 53, 133, 29, 59, 1892891, 1, 17, 10787, 1, 781, 4670029, 1, 1, 553, 7667, 83, 113477, 1, 2047, 45353, 47, 1, 150059, 1, 1111, 721, 53, 107, 6973057, 253, 55709, 7

Offset: 1

Author

Paul Curtz, Oct 01 2009

Keywords

• nonn

Crossrefs

Cf. A124886.

Programs

Maple

A165734 := proc(n) op( 1+(n mod 2),[30,6]) ; end:
A027762 := proc(n) a := 0 ; p := 2 ; while p-1 <= 2*n do if (2*n) mod (p-1) = 0 then a := a+1/p ; fi; p := nextprime(p) ; od: denom(a) ; end:
A165949 := proc(n) A027762(n)/A165734(n) ; end: seq(A165949(n),n=1..80) ; # R. J. Mathar, Oct 05 2009

Mathematica

a[n_] := Numerator[ Denominator[ BernoulliB[2*n, 1/2]]/(3*5*2^(2*n))]; Array[a, 57] (* Jean-François Alcover, Apr 17 2013, after Paul Curtz *)

Extensions

Extended by R. J. Mathar, Oct 05 2009