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 A336720 #4 Aug 24 2020 23:25:54 %S A336720 3,7,31,127,8191,131071,524287,2147483647,4432676798593, %T A336720 2305843009213693951,57912614113275649087721, %U A336720 618970019642690137449562111,162259276829213363391578010288127,170141183460469231731687303715884105727,79638304766856507377778616296087448490695649 %N A336720 A336719 with duplicates removed. %C A336720 Also, record values in A005420. %C A336720 Mersenne primes (A000668) are a subsequence. %C A336720 For the corresponding orders of 2 (exponents), see A336721. %o A336720 (PARI) re=0;for(k=2,+oo,p=vecmax(factor(2^k-1)[,1]);if(p>re,re=p;print1(re,", "))) %Y A336720 Cf. A000668, A005420, A336719, A336721. %K A336720 nonn %O A336720 1,1 %A A336720 _Jeppe Stig Nielsen_, Aug 01 2020