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 A119563 #8 Oct 01 2013 17:58:25 %S A119563 2,5,19,263,65551,4294967327,18446744073709551679, %T A119563 340282366920938463463374607431768211583, %U A119563 115792089237316195423570985008687907853269984665640564039457584007913129640191 %N A119563 Define F(n) = 2^(2^n)+1 = n-th Fermat number, M(n) = 2^n-1 = the n-th Mersenne number. Then a(n) = F(n)+M(n)-1 = 2^(2^n) + 2^n - 1. %C A119563 The first 5 entries are primes. Are there infinitely many primes in this sequence? %F A119563 a(n) = A119561(n)-2=A000215(n)+A000225(n)-1. - _R. J. Mathar_, Apr 22 2007 %e A119563 F(2) = 2^(2^2)+1 = 17, M(2) = 2^2-1 = 3, F(2)+ M(2) - 1 = 19 %o A119563 (PARI) fm3(n) = for(x=0,n,y=2^(2^x)+2^x-1;print1(y",")) %K A119563 nonn %O A119563 0,1 %A A119563 _Cino Hilliard_, May 31 2006 %E A119563 Edited by _N. J. A. Sloane_, Jun 03 2006