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Numbers k such that k and k^2 use only the digits 2, 4, 8 and 9.
0

%I #14 Feb 03 2025 09:39:17

%S 2,22,222,288,49898882,499898882

%N Numbers k such that k and k^2 use only the digits 2, 4, 8 and 9.

%C Generated with DrScheme.

%C No additional terms up to 10^12. - _Harvey P. Dale_, Oct 11 2017

%H Jonathan Wellons, <a href="https://web.archive.org/web/20090206165028/http://jonathanwellons.com/shared-digits/">Tables of Shared Digits</a> [archived]

%e 499898882^2 = 249898892224849924.

%t With[{c={2,4,8,9}},Select[FromDigits/@Flatten[Table[Tuples[c,n],{n,10}],1],SubsetQ[c,IntegerDigits[#^2]]&]] (* _Harvey P. Dale_, Oct 11 2017 *)

%K base,nonn,more

%O 1,1

%A Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008