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 A265148 #10 Oct 13 2017 03:31:12
%S A265148 4,9,61,504,4516,47504,382025,3975209,33057329,80214016,454665681,
%T A265148 4507966404,44168848384,69005350809,163894140625,784386132324,
%U A265148 5954843762641,7954794246144,53996843222416,69176076458289,379510987739761,1641640879622564,7593632535763529,31733339799107600
%N A265148 a(1) = 4, a(n) = smallest number > a(n-1) such that the concatenation of a(n-1) and a(n) is a square.
%e A265148 a(3) is 61 since it is the least number greater than a(2)=9 which concatenated with 9 forms a perfect square, i.e., 961 = 31^2.
%t A265148 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, 4, 23] (* after the algorithm of _David W. Wilson_ in A090566 *)
%Y A265148 Cf. A090566, A265147, A265149, A265150, A265151, A265152, A265153, A265154, A265155.
%K A265148 nonn,base
%O A265148 1,1
%A A265148 _Robert G. Wilson v_, Dec 02 2015