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 A037919 #12 Jun 15 2022 13:15:47 %S A037919 4,2,2,2,11,211 %N A037919 Trajectory of 4 under prime factor concatenation procedure. %H A037919 Patrick De Geest, <a href="http://www.worldofnumbers.com/topic1.htm">Home Primes</a> %e A037919 May be regarded as the rows of an irregular triangle: %e A037919 4 %e A037919 2 2 %e A037919 2 11 %e A037919 211. - _N. J. A. Sloane_, Jun 15 2022 %Y A037919 Cf. A037273. %K A037919 fini,full,nonn,tabf,base %O A037919 0,1 %A A037919 _Jeff Burch_ %E A037919 Edited by _Charles R Greathouse IV_, Apr 30 2010