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 A116281 #13 Jul 18 2021 06:46:58 %S A116281 39,57,32262231,67737765,79321055,3341093417798787499092, %T A116281 3861488851737861033960,4747922651210186579786,5252077348789813420210, %U A116281 6138511148262138966036,6658906582201212500904,7232275368591793618230 %N A116281 Numbers k such that k*(k+5) gives the concatenation of two numbers m and m-1. %e A116281 79321055 * 79321060 = 62918301//62918300, where // denotes concatenation. %Y A116281 Cf. A028557, A116112, A116276, A116280, A116282, A116289. %K A116281 nonn,base %O A116281 1,1 %A A116281 _Giovanni Resta_, Feb 06 2006