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 A115530 #8 Jul 15 2021 06:28:42 %S A115530 5714285714285714286,8571428571428571429,11428571428571428572, %T A115530 465116279069767441860465116279070,511627906976744186046511627906977, %U A115530 558139534883720930232558139534884,604651162790697674418604651162791 %N A115530 Numbers k such that k^2 is the concatenation of two numbers 2*m and m. %e A115530 5714285714285714286^2 = 3265306122448979592_1632653061224489796. %Y A115530 Cf. A102567, A106497, A115527 - A115556. %K A115530 nonn,base %O A115530 1,1 %A A115530 _Giovanni Resta_, Jan 25 2006 %E A115530 Definition modified by _Georg Fischer_, Jul 25 2019