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Smallest m>0 such that (2n-1)2^m+1 is prime, or -1 if no such value exists.
7

%I #13 Mar 30 2014 04:54:20

%S 1,1,1,2,1,1,2,1,3,6,1,1,2,2,1,8,1,1,2,1,1,2,2,583,2,1,1,4,2,5,4,1,1,

%T 2,1,3,2,1,3,2,1,1,4,2,1,8,2,1,2,1,3,16,1,3,6,1,1,2,3,1,8,6,1,2,3,1,4,

%U 1,3,2,1,53,6,8,3,4,1,1,8,6,3,2,1,7,2,8,1,2,2,1,4,1,3,6,1,1,2,4,15,2

%N Smallest m>0 such that (2n-1)2^m+1 is prime, or -1 if no such value exists.

%C There exist odd integers 2k-1 such that (2k-1)2^n+1 is always composite.

%D Ribenboim, P. The New Book of Prime Number Records. New York: Springer-Verlag, pp. 357-359, 1996.

%H T. D. Noe, <a href="/A033809/b033809.txt">Table of n, a(n) for n=1..1000</a>

%Y Cf. A046067 (except for initial term a(1) identical to this sequence), A046068, A046069, A046070.

%Y Cf. A040076

%K sign

%O 1,4

%A _Eric W. Weisstein_