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 A336721 #6 Aug 24 2020 23:26:02 %S A336721 2,3,5,7,13,17,19,31,49,61,83,89,107,127,167,179,197,233,241,269,281, %T A336721 347,373,421,443,457,487,521,607,697,769,829,881,1049,1063 %N A336721 Values k where A336719(k) increases. %C A336721 Also, values k (record positions) where A005420(k) reaches a new maximum. For the maximum itself, see A336720. %C A336721 A000043 is a subsequence. %o A336721 (PARI) re=0;for(k=2,+oo,p=vecmax(factor(2^k-1)[,1]);if(p>re,re=p;print1(k,", "))) %Y A336721 Cf. A000043, A005420, A336719, A336720. %K A336721 nonn,hard,more %O A336721 1,1 %A A336721 _Jeppe Stig Nielsen_, Aug 01 2020