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 A137117 #17 May 10 2024 11:28:35
%S A137117 5,27,77,527,7227,27797977
%N A137117 Numbers k such that k and k^2 use only the digits 2, 5, 7 and 9.
%C A137117 Generated with DrScheme.
%C A137117 No further terms up to 10^12. - _Harvey P. Dale_, Oct 02 2017
%C A137117 No further terms up to 10^38. - _Michael S. Branicky_, May 27 2021
%H A137117 Jonathan Wellons, <a href="https://web.archive.org/web/20090206165028/http://jonathanwellons.com/shared-digits/">Tables of Shared Digits</a> [archived].
%e A137117 27797977^2 = 772727525292529.
%t A137117 With[{c={2,5,7,9}},Table[Select[FromDigits/@Tuples[c,n],SubsetQ[c, IntegerDigits[ #^2]]&],{n,8}]]//Flatten (* _Harvey P. Dale_, Oct 02 2017 *)
%o A137117 (Python) # uses auptod in A137110
%o A137117 print(auptod(16, only="2579")) # _Michael S. Branicky_, May 27 2021
%Y A137117 Cf. A137110, A137116.
%K A137117 base,nonn,more
%O A137117 1,1
%A A137117 Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008