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 A048352 #20 Mar 06 2025 10:53:34
%S A048352 24,76,424,3576,8819,88924,278874,2116076,8819154,61463576,277450424,
%T A048352 526087234,1943470576,21858013924,199694210926,260341642412,
%U A048352 3574601764924,11156736878576,27180356468924,275640849218286,1130388343790654,8818036509210958,57251968301165924,75972671255970576,841288938282667412
%N A048352 a(n)^2 is the smallest square containing exactly n 7's.
%H A048352 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SquareNumber.html">Square Number</a>
%t A048352 a[n_] := Module[{i = 1}, While[DigitCount[i^2][[7]] != n, i++ ]; i]; (* Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 22 2006 *)
%Y A048352 Cf. A036514, A034990.
%K A048352 nonn,base
%O A048352 1,1
%A A048352 _Patrick De Geest_, Mar 15 1999
%E A048352 a(13)-a(16) from _Jon E. Schoenfield_, Jan 24 2009
%E A048352 a(17)-a(19) from _Giovanni Resta_, Jul 27 2018
%E A048352 a(20)-a(25) from _Max Alekseyev_, Mar 06 2025