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 A158912 #5 Oct 04 2012 16:26:59 %S A158912 20,1218,7540,20280,1373090,4903600,23308460,316540365,527813814, %T A158912 4091661910,16718044954,1034412600,142903074740,1827252574658, %U A158912 31036383127940 %N A158912 Primitive numbers n whose square can be represented as a four "digit" repdigit number in some base < n. %e A158912 20^2 = 1111 in base 7 %e A158912 1218^2 = (21)(21)(21)(21) in base 41 %e A158912 7540^2 = (58)(58)(58)(58) in base 99 %Y A158912 A158235, A158245 %K A158912 nonn,base %O A158912 1,1 %A A158912 _T. D. Noe_, Mar 30 2009