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 A034990 #11 Oct 09 2019 03:03:28
%S A034990 27,88,882,8819,278886,881917,8819171,8819171,2788866754,2788866755,
%T A034990 27888667551,881917103688,8819171036882,278886675511358,
%U A034990 2788866755113584,27888667551135851,88191710368819686,278886675511358516,8819171036881968635,8819171036881968635
%N A034990 a(n)^2 is smallest square starting with a string of n 7's.
%D A034990 David Wells, 'Curious and Interesting Numbers', Penguin Books 1988, p. 184.
%e A034990 a(5) = 278886^2 = {77777}400996.
%Y A034990 Cf. A034991.
%K A034990 nonn,base
%O A034990 1,1
%A A034990 _Patrick De Geest_, Nov 15 1998
%E A034990 More terms from Francisco Salinas (franciscodesalinas(AT)hotmail.com), Dec 23 2001
%E A034990 a(18) corrected and a(19), a(20) added by John Tomko, Nov 14 2006