This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A260758 #5 Aug 01 2015 17:13:33 %S A260758 1,1,1,2,1,3,10,5,1,3,14,11,4,5,4,5,8,30,2,6,1,8,29,12,29,30,11,2,4,5, %T A260758 19,29,2,9,7,11,4,74,16,24,8,18,10,30,56,15,35,24,4,35,19,111,19,18,1, %U A260758 57,8,20,14,2,2,48,29,26,92,24,19,155,2,78,35,56,113,33,70,32,7 %N A260758 Least k > 0 such that M(n)^2 + 2k is prime, where M(n) = 2^n - 1 = A000225(n). %e A260758 M(0)^2 + 2*1 = 0 + 2 = 2 is prime, thus a(0)=1. %e A260758 M(1)^2 + 2*1 = 1 + 2 = 3 is prime, thus a(1)=1. %e A260758 M(2) = 2^2-1 = 3 and 3*3 + 2k = 11 is a prime for k=1, thus a(2) = 1. %e A260758 M(3) = 2^3-1 = 7 and 7*7 + 2k = 53 is a prime for k=2 but not for k=1, thus a(3) = 2. %e A260758 M(4) = 2^4-1 = 15 and 15*15 + 2k = 227 is a prime for k=1, thus a(4) = 1. %o A260758 (PARI) a(n)=for(k=1,9e9,ispseudoprime((2^n-1)^2+2*k)&&return(k)) %Y A260758 Cf. A260757. %K A260758 nonn %O A260758 0,4 %A A260758 _M. F. Hasler_, Jul 30 2015