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 A210015 #10 Jun 10 2016 00:21:00 %S A210015 1203,1230,1302,2013,2031,2103,2130,3012,3021,3102,3120 %N A210015 In base 4, numbers n which have 4 distinct digits, do not start with 0, and have property that the product (written in base 4) of any two adjacent digits is a substring of n. %C A210015 Computed by Jean-Paul Davalan. %C A210015 The analog in base 2 is 10; in base 3, 102,120,201,210. %H A210015 Eric Angelini, <a href="http://www.cetteadressecomportecinquantesignes.com/DixChiffres.htm">10 different digits, 9 products</a> %H A210015 E. Angelini, <a href="/A198298/a198298.pdf">10 different digits, 9 products</a> [Cached copy, with permission] %Y A210015 A generalization of A198298. Cf. A210013-A210020, A203569, A203566. %K A210015 nonn,base,fini,full %O A210015 1,1 %A A210015 _N. J. A. Sloane_, Mar 16 2012