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 A116502 #16 Oct 14 2024 18:08:54
%S A116502 69696,56722567225,95540955409,1108033241108033241,
%T A116502 1220096161220096161,4312080784312080784,4432132964432132964,
%U A116502 4880384644880384644,9024307889024307889,9972299169972299169,946308825294630882529,11542927396115429273961,46171709584461717095844
%N A116502 Squares with structure dmdmd, where d is a single digit and m a string of digits.
%H A116502 Giovanni Resta, <a href="/A116502/b116502.txt">Table of n, a(n) for n = 1..300</a>
%H A116502 Erich Friedman, <a href="https://erich-friedman.github.io/puzzle/mathpuzzle">Puzzles of the Week</a> [_N. J. A. Sloane_, Mar 12 2011]
%F A116502 a(n) = A116501(n)^2.
%e A116502 309097^2 = a(3) = 9[5540]9[5540]9.
%t A116502 w={}; Do[s = Reduce[(1 + 10^(1+e) + 100^(1+e)) d + 10 (1+10^(1+e)) x == y^2 && 0 <= x < 10^e && y>0, {x,y}, Integers]; If[s =!= False, w = Union[w, y^2 /. List@ ToRules@ s]], {e, 12}, {d, 9}]; w (* _Giovanni Resta_, Aug 01 2018 *)
%Y A116502 Cf. A116500, A116501, A069919.
%K A116502 base,nonn
%O A116502 1,1
%A A116502 _Giovanni Resta_, Feb 18 2006
%E A116502 a(11)-a(13) from _Giovanni Resta_, Aug 01 2018