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 A058421 #18 Mar 08 2024 09:03:03
%S A058421 1,9,109,901,1009,9001,10009,10401,90001,100009,100901,900001,1000009,
%T A058421 1004001,8954391,9000001,10000009,10009001,34351141,90000001,
%U A058421 100000009,100040001,900000001,1000000009,1000090001,3163554991,9000000001,10000000009,10000400001
%N A058421 Numbers k such that k^2 contains only digits {0,1,8}, not ending with zero.
%H A058421 Zhao Hui Du, <a href="/A058421/b058421.txt">Table of n, a(n) for n = 1..91</a>
%H A058421 Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Index to related sequences</a>
%H A058421 Hisanori Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#018">Sporadic tridigital solutions</a>
%Y A058421 Cf. A058422.
%K A058421 nonn,base
%O A058421 1,2
%A A058421 _Patrick De Geest_, Nov 15 2000
%E A058421 Terms a(28) and above from _Zhao Hui Du_, Mar 07 2024