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 A265149 #9 Oct 13 2017 03:30:59
%S A265149 8,41,209,764,5225,8441,9344,63761,82201,477264,3191044,4038489,
%T A265149 34656049,61233321,271005625,3465072801,36565416324,83511106624,
%U A265149 222222321476,425286636356,2743260628100,9534841632400,33984728488004,128198574830929,741089622057984,5579432351776489
%N A265149 a(1) = 8, a(n) = smallest number > a(n-1) such that the concatenation of a(n-1) and a(n) is a square.
%e A265149 a(3) is 209 since it is the least number greater than a(2)=41 which concatenated with 41 forms a perfect square, i.e., 41209 = 203^2.
%t A265149 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, 8, 25] (* after the algorithm of _David W. Wilson_ in A090566 *)
%Y A265149 Cf. A090566, A265147, A265148, A265150, A265151, A265152, A265153, A265154, A265155.
%K A265149 nonn,base
%O A265149 1,1
%A A265149 _Robert G. Wilson v_, Dec 02 2015