%I #4 Mar 31 2012 13:22:04
%S 1,5,1,11,9,89,25,359,187,11,145,309,559,47,115,41,87,1169,271,41,565,
%T 1005,1231,245,783,185,61,431,153,1205,423,465,2547,1257,891,351,25,
%U 945,937,431,453,4221,2763,251,783,1761,1381,2493,2125,5241,2871,255,4507
%N Least odd k such that (k*2^n)^2+k*2^n-1 is the first of twin primes with n>0.
%e (1*2^1)^2+1*2^1-1=5, 5 and 7 twin primes so k(1)=1
%e (1*2^2)^2+1*2^2-1=19 prime but 21 not prime
%e (3*2^2)^2+3*2^2-1=155 not prime
%e (5*2^2)^2+5*2^2-1=419, 419 and 421 twin primes so k(2)=5
%K nonn
%O 1,2
%A _Pierre CAMI_, Apr 09 2006