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 A116231 #9 Jul 18 2021 02:49:03 %S A116231 7,63,42752,57240,75422,425071,574921,979527,4301392,5698600,7028665, %T A116231 4925000746,5074999246,7748266573,8511881483,8814851183,7059602159671, %U A116231 7106167933827,7439286611620,7485852385776,46791112884924 %N A116231 Numbers k such that k*(k+9) gives the concatenation of two numbers m and m-9. %Y A116231 Cf. A116193, A116230, A116240. %K A116231 nonn,base %O A116231 1,1 %A A116231 _Giovanni Resta_, Feb 06 2006