%I #7 Mar 30 2012 18:38:53
%S 16,335,8399,12599,16383,62999,546359,743999,2815199,3046655,3592655,
%T 8422679,25357439,26356199,29318279,75428999,112039199,202417343,
%U 226325999,329611559,335894159,452921039
%N Composite n such that sigma(2n+1)-sigma(n)=n+1.
%C Primes satisfying sigma(2p+1)-sigma(p)=p+1 are Sophie Germain primes A005384(n)
%o (PARI) for(n=1,500000000, if((sigma(2*n+1)-sigma(n)==n+1) && (!isprime(n)), print1(n,",")))
%K easy,nonn
%O 1,1
%A _Benoit Cloitre_, Feb 28 2002
%E More terms from _Rick L. Shepherd_, May 08 2002