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 A115544 #6 Jul 15 2021 09:16:28 %S A115544 4,142857142857142857142857142857142858, %T A115544 285714285714285714285714285714285716, %U A115544 142857142857142857142857142857142857142857142857142857142857142857142857142858 %N A115544 Numbers k such that k^2 is the concatenation of two numbers m and 6*m. %e A115544 4^2 = 1_6. %Y A115544 Cf. A102567, A106497, A115527 - A115556. %K A115544 nonn,base %O A115544 1,1 %A A115544 _Giovanni Resta_, Jan 25 2006