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 A115542 #9 Jul 15 2021 09:15:17 %S A115542 7142857142857142857143,14285714285714285714286, %T A115542 21428571428571428571429, %U A115542 730337078651685393258426966292134831460674157303370786517 %N A115542 Numbers k such that k^2 is the concatenation of two numbers 5*m and m. %e A115542 7142857142857142857143^2 = 5102040816326530612245_1020408163265306122449. %Y A115542 Cf. A102567, A106497, A115527 - A115556. %K A115542 nonn,base %O A115542 1,1 %A A115542 _Giovanni Resta_, Jan 25 2006 %E A115542 Definition modified by _Georg Fischer_, Jul 26 2019