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 A046270 #5 Oct 10 2019 00:35:26 %S A046270 0,0,0,0,5,2,409,163,6553,2621,857,419,1677721,71,43,107,4294967, %T A046270 171798691,6871947673,779069,511627,4398046511,18604441,703687441, %U A046270 28147497671,11258999,59962737049,180143985094819,759403792793 %N A046270 Largest prime substring in 4^n (0 if none). %Y A046270 Cf. A046262. %K A046270 nonn %O A046270 0,5 %A A046270 _Patrick De Geest_, Jun 15 1998