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 A037921 #7 Aug 11 2024 14:41:30 %S A037921 9,3,3,3,11,311 %N A037921 Trajectory of 9 under prime factor concatenation procedure. %H A037921 P. De Geest, <a href="https://www.worldofnumbers.com/topic1.htm">Home Primes</a> %e A037921 9 -> 3,3 -> 3,11 -> 311 %Y A037921 Cf. A037274, A037273. %K A037921 fini,full,nonn,tabf,base %O A037921 1,1 %A A037921 _Jeff Burch_ %E A037921 Edited by _Charles R Greathouse IV_, Apr 30 2010