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 A115447 #5 Jun 18 2021 18:09:29 %S A115447 71,7235,9701,798981,997001,35324118,64675883,99970001,3297392379, %T A115447 6702607622,7890726434,8812181189,9999700001,897807218979, %U A115447 917811219179,979998999801,999997000001,46193210013657,49751928874867 %N A115447 Numbers whose square is the concatenation of two numbers k and k-9. %e A115447 638370_638361 = 798981^2. %Y A115447 Cf. A030467, A106497, A115436, A115427, A115438, A115439, A115440, A115441, A115442, A115443, A115444, A115445, A115446. %K A115447 base,nonn %O A115447 1,1 %A A115447 _Giovanni Resta_, Jan 25 2006