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 A265147 #11 Oct 13 2017 03:30:51
%S A265147 2,5,29,241,1809,6516,27729,70281,191236,537636,5052601,24352064,
%T A265147 50491721,335176900,816286736,1584582656,5835352241,31064957504,
%U A265147 299026078001,368254999225,916181280225,6283970794161,31966212255489,247575988078441,558234718638336,4773574731628096
%N A265147 a(1) = 2, a(n) = smallest number > a(n-1) such that the concatenation of a(n-1) and a(n) is a square.
%e A265147 a(3) is 29 since it is the least number greater than a(2)=5 which concatenated with 5 forms a perfect square, i.e., 529 = 23^2.
%t A265147 f[n_] := Block[{x = n, d = 1 + Floor@ Log10@ n}, q = (Floor@ Sqrt[(10^d + 1) x] + 1)^2; If[q < (10^d) (x + 1), Mod[q, 10^d], Mod[(Floor@ Sqrt[(10^d)(10x + 1) - 1] + 1)^2, 10^(d + 1)] ]]; NestList[f, 2, 25] (* after the algorithm of _David W. Wilson_ in A090566 *)
%Y A265147 Cf. A090566, A265148, A265149, A265150, A265151, A265152, A265153, A265154, A265155.
%K A265147 nonn,base
%O A265147 1,1
%A A265147 _Robert G. Wilson v_, Dec 02 2015