%I #16 Sep 26 2016 06:15:06
%S 5,31,41,31,61,3421,5,557,821,371,121,3421,5,929,15745,557,5,2557843,
%T 5,15541,1805,743,241,60887,61,1673,821,929,301,79085411,5,557,66961,
%U 31,4397,188641729,5,31,3281,277727,421,4462547,5,66817,313477,1487,5,5952449
%N Numerator of sum_{p prime, p-1 divides 2*n} 1/p.
%H Seiichi Manyama, <a href="/A027761/b027761.txt">Table of n, a(n) for n = 1..10000</a>
%t a[n_] := Sum[ Boole[ PrimeQ[d+1] ]/(d+1), {d, Divisors[2n]}] // Numerator; Table[a[n], {n, 1, 48}] (* _Jean-François Alcover_, Aug 10 2012 *)
%o (PARI)
%o a(n)=
%o {
%o my(bd=0);
%o forprime (p=2, 2*n+1, if( (2*n)%(p-1)==0, bd += 1/p; ) );
%o bd = numerator(bd);
%o return(bd);
%o }
%o /* _Joerg Arndt_, May 06 2012 */
%Y Cf. A027762.
%K nonn,frac
%O 1,1
%A _N. J. A. Sloane_.