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 A050728 #5 Oct 16 2019 01:20:27 %S A050728 0,1,2,3,4,5,7,8,9,10,12,17,27 %N A050728 Decimal expansion of 7^n contains no pair of consecutive equal digits (probably finite). %e A050728 7^27 = 65712362363534280139543. %Y A050728 Cf. A030703, A046265, A046273. %K A050728 nonn,base %O A050728 0,3 %A A050728 _Patrick De Geest_, Sep 15 1999