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 A116279 #9 Jul 18 2021 02:56:58 %S A116279 36363636363,45454545454,54545454545,63636363636,72727272727, %T A116279 81818181818,90909090909,428571428571428571428,571428571428571428571, %U A116279 714285714285714285714,857142857142857142857 %N A116279 Numbers k such that k*(k+2) gives the concatenation of two numbers m and m-1. %e A116279 36363636363 * 36363636365 = 13223140496//13223140495, where // denotes concatenation. %Y A116279 Cf. A102567, A116273, A116280, A116286. %K A116279 nonn,base %O A116279 1,1 %A A116279 _Giovanni Resta_, Feb 06 2006