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 A048347 #29 Mar 06 2025 10:41:12
%S A048347 5,15,149,1415,4585,14585,105935,364585,3496101,4714045,34964585,
%T A048347 149305935,1490725415,4714469665,1490711985,149071333335,
%U A048347 1105537083332,1489973900149,15106363633335,47140462469223,450246846657722,1490713327333335,4714049454791668,47129833685493335,27788886667555111
%N A048347 a(n)^2 is the smallest square containing exactly n 2's.
%H A048347 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SquareNumber.html">Square Number</a>
%e A048347 From _Jon E. Schoenfield_, Dec 25 2008: (Start)
%e A048347 a(16) = 149071333335 = sqrt(22222262422274682222225);
%e A048347 a(17) = 1105537083332 = sqrt(1222212242622225512222224);
%e A048347 a(18) = 1489973900149 = sqrt(2220022223125222222222201). (End)
%e A048347 From _Giovanni Resta_, Jul 27 2018: (Start)
%e A048347 a(19) = 15106363633335 = sqrt(228202222222546222323222225);
%e A048347 a(20) = 47140462469223 = sqrt(2222223201812222222222223729). (End)
%t A048347 a[n_] := Block[{k=1}, While[DigitCount[k^2, 10, 2] != n, k++]; k]; Array[a, 7] (* _Giovanni Resta_, Jul 27 2018 *)
%Y A048347 Cf. A036509, A034980.
%K A048347 nonn,base
%O A048347 1,1
%A A048347 _Patrick De Geest_, Mar 15 1999
%E A048347 a(13)-a(15) from _Max Alekseyev_, Oct 20 2008, Nov 10 2008, Dec 05 2008
%E A048347 a(16)-a(18) from _Jon E. Schoenfield_, Dec 25 2008
%E A048347 a(19)-a(20) from _Giovanni Resta_, Jul 27 2018
%E A048347 a(21)-a(25) from _Max Alekseyev_, Mar 06 2025