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 A115555 #11 Jul 15 2021 09:11:27 %S A115555 1836734693877551020408163265306122449, %T A115555 7346938775510204081632653061224489796, %U A115555 15311909262759924385633270321361058601134215500945179584121,27221172022684310018903591682419659735349716446124763705104 %N A115555 Numbers k such that the concatenation of 9*k with k gives a square. %Y A115555 Cf. A102567, A106497, A115527 - A115556. %K A115555 nonn,base %O A115555 1,1 %A A115555 _Giovanni Resta_, Jan 25 2006