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 A199630 #19 Aug 23 2023 13:27:55
%S A199630 3175462089,3175804269,3204957816,3206549178,3210754689,3254196708,
%T A199630 3260974851,3275409816,3284591706,3290581476,3406829517,3410856297,
%U A199630 3459186720,3469857012,3475806912,3501249678,3512067849,3519876240,3549716208,3564980172,3587902614
%N A199630 Numbers having each digit once and whose square has each digit twice.
%H A199630 T. D. Noe, <a href="/A199630/b199630.txt">Table of n, a(n) for n = 1..534</a> (all terms).
%H A199630 Patrick De Geest, <a href="http://www.worldofnumbers.com/ninedig4.htm">The nine digits (page 4) with some ten digit (pandigital) exceptions</a>
%H A199630 Author?, <a href="http://web.archive.org/web/20080708203024/http://blue.kakiko.com/mmrmmr/htm/eqtn11.html">All terms</a>
%e A199630 3175462089^2 = 10083559478676243921.
%t A199630 t = Select[Permutations[Range[0, 9]], #[[1]] > 0 &]; t2 = Select[t, Union[DigitCount[FromDigits[#]^2]] == {2} &]; FromDigits /@ t2
%Y A199630 Cf. A050278 (pandigital numbers), A199631, A365144, A199632, A199633. Subsequence of A114258.
%K A199630 nonn,base,fini,full
%O A199630 1,1
%A A199630 _T. D. Noe_, Nov 09 2011