%I #7 Mar 31 2012 13:22:06
%S 1,2,1,1,3,2,3,1,1,9,8,7,6,5,14,8,1,8,14,10,11,10,6,10,14,2,23,10,11,
%T 81,8,3,33,8,22,8,1,6,7,31,19,43,10,1,12,3,23,4,1,3,61
%N The smallest index k such that prime(k) *2^n *( prime(k)*2^n -1)-1 is prime.
%C Let S(n) = sum_{k=1..n} a(k) be the partial sums. Then S(n) ~ c*A000217(n) for large n where c is a constant near 0.435.
%H Pierre CAMI, <a href="/A179205/b179205.txt">Table of n, a(n) for n = 1...8000</a>
%e 2*2*(2*2-1)-1=11 prime so k(1)=1 as 2=p(1) 2*2^2*(2*2^2-1)-1=55 composite 3*2^2*(3*2^2-1)=131 prime so k(2)=2 as 3=p(2)
%K nonn
%O 1,2
%A _Pierre CAMI_, Jul 02 2010