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 A274509 #11 Jul 06 2016 00:55:39 %S A274509 0,1,3,7,2,5,6,4,3,9,15,13,17,11,8,19,18,11,9,4,16,5,23,24,17,19,17,5, %T A274509 36,6,32,23,34,40,41,39,25 %N A274509 a(n) is the only number m such that 5^(2^m) + 1 is divisible by A273946(n). %o A274509 (PARI) forstep(p=3, 10^15, 2, if(!Mod(p, 5)==0, if(isprime(p), o=znorder(Mod(5, p)); x=ispower(2*o); if(2^(x-1)==o, print1(x-2, ", "))))); %Y A274509 Cf. A273946. %K A274509 nonn,more %O A274509 1,3 %A A274509 _Arkadiusz Wesolowski_, Jun 25 2016