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 A265154 #9 Oct 13 2017 03:32:11
%S A265154 16,81,225,625,681,2100,3889,17841,33121,452049,2561025,9392964,
%T A265154 9776361,69946276,104857889,232947041,619807376,729085444,5435467076,
%U A265154 8236728484,52686818481,370961353041,3290130736249,4333224368201,44310474545225,67348431045184,67835332918689
%N A265154 a(1) = 16, a(n) = smallest number > a(n-1) such that the concatenation of a(n-1) and a(n) is a square.
%e A265154 a(3) is 225 since it is the least number greater than a(2)=81 which concatenated with 81 forms a perfect square, i.e., 81225 = 285^2.
%t A265154 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, 16, 25] (* after the algorithm of _David W. Wilson_ in A090566 *)
%Y A265154 Cf. A090566, A265147, A265148, A265149, A265150, A265151, A265152, A265153, A265155.
%K A265154 nonn,base
%O A265154 1,1
%A A265154 _Robert G. Wilson v_, Dec 02 2015