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%I #5 Mar 31 2012 12:38:36
%S 4,12,24,30,30,66,954,1920,30,4116,576,214608
%N The smallest positive k such that the n-th Mersenne prime +-k are two primes.
%C Smallest k>0 such that A000668(n)+k and A000668(n)-k are both prime.
%F a(n) = A082467(A000668(n)). - R. J. Mathar, Jan 23 2011
%e 7+-4->primes, 31+-12->primes, 127+-24->primes, 8191+-30->primes, 131071+-30->primes, 524287+-66->primes..
%t g[n_]:=2^Prime[n]-1; f[n_]:=Block[{k},If[OddQ[n],k=2,k=1];While[ !PrimeQ[n-k]||!PrimeQ[n+k],k+=2];k]; lst={};Do[If[PrimeQ[g[n]],AppendTo[lst,f[g[n]]]],{n,2,40}];lst
%Y Cf. A000668, A082467.
%K nonn
%O 2,1
%A _Vladimir Joseph Stephan Orlovsky_, May 09 2010
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