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 A350918 #19 Jan 28 2022 23:06:14
%S A350918 9801,998001,99980001,9048004641,9999800001,923594037444,989444005264,
%T A350918 999998000001,7901234409876544,8434234407495744,8934133805179209,
%U A350918 9999999800000001,999999998000000001,79012345680987654321,82644628100826446281,83407877440792003584,87138706300620940900
%N A350918 Numbers k = x.y which when split into two parts x and y of equal length, added and squared result in the same number k, '.' means concatenation, and the second part y starts with 0.
%C A350918 Problem proposed on French site Diophante (see link).
%H A350918 Diophante, <a href="http://www.diophante.fr/problemes-par-themes/arithmetique-et-algebre/a1-pot-pourri/1024-a1945-concatenations-en-tous-genres">A1945 - Concaténations en tous genres</a> (in French).
%e A350918 (998+001)^2 = 999^2 = 998001, as x = 998 and y = 001 starts with 0, 998001 is a term.
%e A350918 (30+25)^2 = 55^2 = 3025, here x = 30 but y = 25 does not start with 0, hence 3025 is not a term.
%Y A350918 Equals A238237 \ A350870.
%Y A350918 A059988 \ {0, 81} is a subsequence.
%K A350918 nonn,base
%O A350918 1,1
%A A350918 _Bernard Schott_, Jan 22 2022