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 A116297 #7 Jul 18 2021 02:55:29 %S A116297 2,5,43,54,38161,61836,83616,346978,653019,950049,8647553,9534263, %T A116297 8167822281,9007920990,9209900790,9950000499,4737445289219, %U A116297 4990568257185,5009431742812,5262554710778,8373808925583 %N A116297 Numbers k such that k*(k+4) gives the concatenation of two numbers m and m+1. %Y A116297 Cf. A115428, A116288, A116296, A116298, A116317. %K A116297 nonn,base %O A116297 1,1 %A A116297 _Giovanni Resta_, Feb 06 2006