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 A046423 #11 Oct 15 2019 12:04:53 %S A046423 25,35,56,62,69,72,76,85,90,100,114,125,138,143,152,189,213,221,238, %T A046423 250,259,260,270,275,278,303,318,333,364,366,369,390,403,441,448,454, %U A046423 469,470,473,485,507,512,519,522,529,559,560,572,588,591,624,629,648 %N A046423 Numbers requiring 3 steps to reach a prime under the prime factor concatenation procedure. %H A046423 Patrick De Geest, <a href="http://www.worldofnumbers.com/topic1.htm">Home Primes</a> %e A046423 69 = 3*23 -> 323 = 17*19 -> 1719 = 3*3*191 and 33191 is prime. %Y A046423 Cf. A037271, A046411. %K A046423 nonn,base %O A046423 1,1 %A A046423 _Patrick De Geest_, Jun 15 1998 %E A046423 Edited by _Charles R Greathouse IV_, Apr 28 2010