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%I #2 Mar 30 2012 17:29:59
%S 2,4,10,4,46,22,16,46,66,136,166,124,636,550,1474,3066,1656,1816,3708,
%T 9436,1746,3696,11262,40138,25900,20808,60340,58818
%N Nearest k to j such that k*(2^j-1)+1 is prime where j=A000043(n) and 2^j-1 = Mersenne-prime(n) = A000668(n). If there are two k values equidistant from j, each of which produces a prime, the larger of the two gets added to the sequence.
%e n=6, j=A000043(6)=17, A000668(6)=131071, then k=12 or k=22 are the nearest values to j which produce primes so we take the larger of the two k values for a(6)=22.
%Y Cf. A000043, A000668, A098556, A101416.
%K hard,nonn
%O 1,1
%A _Ray Chandler_, Apr 16 2009