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%I #12 Apr 12 2024 09:51:27
%S 0,88,878,880,8780,8800,87800,88000,878000,880000,8780000,8800000,
%T 87800000,88000000,878000000,880000000,8780000000,8800000000,
%U 87800000000,88000000000,878000000000,880000000000,8780000000000,8800000000000,87800000000000,88000000000000,878000000000000,880000000000000
%N Numbers k such that k and k^2 use only the digits 0, 4, 7 and 8.
%C Generated with DrScheme.
%C Conjectures: (1) the digit 4 never appears in the terms of the sequence (although it does appear in the digits of the squares of the terms of the sequence), and (2) all nonzero terms are of the form 88 * 10^m or 878 * 10^m. - _Harvey P. Dale_, Oct 24 2020
%H J. Wellons, <a href="https://web.archive.org/web/20090206165028/http://jonathanwellons.com/shared-digits/">Tables of Shared Digits</a> [archived]
%e 878^2 = 770884.
%t With[{c={0,4,7,8}},Select[FromDigits/@Tuples[c,15],SubsetQ[ c,IntegerDigits[ #^2]]&]] (* _Harvey P. Dale_, Oct 24 2020 *)
%K base,nonn
%O 1,2
%A Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008