%I
%S 2,6,4,16,36,6,42,24,172,18,52,54,6,130
%N Least k such that k*Mersenneprime(n)*Mersenneprime(n+1) + 1 is prime.
%e 2*(2^21)*(2^31) + 1 = 43 prime so k(1)=2
%e 2*(2^31)*(2^51) + 1 = 435 composite
%e 4*(2^31)*(2^51) + 1 = 867 composite
%e 6*(2^31)*(2^51) + 1 = 1303 prime so k(2)=6
%K nonn
%O 1,1
%A _Pierre CAMI_, Oct 17 2004
