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 A048349 #19 Mar 06 2025 10:44:59
%S A048349 2,12,38,212,2538,6888,66592,210771,2059962,6696592,21081538,
%T A048349 209868112,664488107,3800598038,18613286762,209820981888,666669703412,
%U A048349 666516649788,6666894662768,49400874945738,156347319914172,210747466045038,5868938950479212,21081850261503238,66666663966850212
%N A048349 a(n)^2 is the smallest square containing exactly n 4's.
%H A048349 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SquareNumber.html">Square Number</a>
%t A048349 a[n_] := Block[{k=1}, While[DigitCount[k^2, 10, 4] != n, k++]; k]; Array[a, 7] (* _Giovanni Resta_, Jul 27 2018 *)
%Y A048349 Cf. A036511, A034984.
%K A048349 nonn,base
%O A048349 1,1
%A A048349 _Patrick De Geest_, Mar 15 1999
%E A048349 More terms from _Jon E. Schoenfield_, Jan 14 2009
%E A048349 a(17)-a(20) from _Giovanni Resta_, Jul 27 2018
%E A048349 a(21)-a(25) from _Max Alekseyev_, Mar 06 2025