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 A036514 #12 Jul 27 2018 08:45:53
%S A036514 576,5776,179776,12787776,77774761,7907477776,77770707876,
%T A036514 4477777637776,77777477275716,3777771174707776,76978737777779776,
%U A036514 276767777777770756,3777077879777771776,477772772701777877776,39877777877357777777476,67777770773777677177744
%N A036514 Smallest square containing exactly n 7's.
%C A036514 a(20) > 10^28. - _Giovanni Resta_, Jul 27 2018
%H A036514 Giovanni Resta, <a href="/A036514/b036514.txt">Table of n, a(n) for n = 1..19</a>
%t A036514 a[n_] := Block[{k=1}, While[DigitCount[k^2, 10, 7] != n, k++]; k]; Array[a, 6] (* _Giovanni Resta_, Jul 27 2018 *)
%Y A036514 Cf. A048352. - _Jon E. Schoenfield_, Jan 24 2009
%K A036514 nonn,base
%O A036514 1,1
%A A036514 _David W. Wilson_
%E A036514 More terms from _Jon E. Schoenfield_, Jan 24 2009
%E A036514 a(16) from _Giovanni Resta_, Jul 27 2018