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 A107709 #8 Mar 31 2012 13:22:04 %S A107709 3,3,3,7,43,19,13,5,571,3,137,59,3823,2707,6277,1063,4523,631,8209, %T A107709 34537,102329,46399,30323,18803,1063,21019 %N A107709 Least odd prime a(n) such that (a(n)*M(n))^2 + a(n)*M(n) - 1 is prime with M(n) = Mersenne-primes (A000043). %e A107709 M(1)=2^2-1=3, (3*3)^2 + 3*3 -1 = 89 prime so a(1)=3 %e A107709 M(2)=2^3-1=7, (3*7)^2 + 3*7 -1 = 461 prime so a(2)=3 %e A107709 M(3)=2^5-1=31, (3*31)^2 + 3*31 -1 = 8741 prime so a(3)=3 %e A107709 M(4)=2^7-1=127,(7*127)^2 + 7*127 -1 = 791209 prime so a(4)=7 %Y A107709 Cf. A000043. %K A107709 hard,more,nonn %O A107709 1,1 %A A107709 _Pierre CAMI_, Jun 10 2005 %E A107709 More terms from Pierre CAMI, Nov 21 2011