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 A058471 #7 Aug 11 2024 14:41:33
%S A058471 3,9949370777987917
%N A058471 Numbers k such that k^2 contains only digits {7,8,9}.
%H A058471 P. De Geest, <a href="https://www.worldofnumbers.com/threedigits.htm">Index to related sequences</a>
%H A058471 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#789">Sporadic tridigital solutions</a>
%Y A058471 Cf. A058472.
%K A058471 nonn,base,hard,more,bref
%O A058471 1,1
%A A058471 _Patrick De Geest_, Nov 15 2000