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 A337431 #5 Sep 25 2020 00:00:09 %S A337431 3,5,7,9,13,14,17,19,26,27,31,33,34,35,37,46,49,51,59,61,62,65,69,74, %T A337431 77,78,82,83,86,89,93,97,103,107,115,118,121,122,123,127,129,130,131, %U A337431 133,137,141,142,143,144,145,147,150,153,154,165,166,169,170,174,175 %N A337431 Numbers k such that the largest prime factor of 2^k - 1 is greater than the largest prime factor of 2^k + 1. %o A337431 (PARI) for(n=2,175,my(p=vecmax(factor(2^n-1)[,1]),q=vecmax(factor(2^n+1)[,1]));if(p>q,print1(n,", "))) %Y A337431 Cf. A002587, A005420, A337430 (complement). %K A337431 nonn %O A337431 1,1 %A A337431 _Hugo Pfoertner_, Sep 23 2020