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Numbers k such that k and k^2 use only the digits 0, 1, 5, 7 and 8.
1

%I #11 Apr 12 2024 09:51:26

%S 0,1,10,100,1000,10000,100000,877501,1000000,1008751,8775010,10000000,

%T 10007751,10087510,87750100,100000000,100077510,100507751,100875100,

%U 877501000,1000000000,1000775100,1005077510,1008751000,1008815501,8775010000,10000000000,10007751000,10050775100,10050775501,10087510000,10088155010,10870057751,87071818501,87750100000

%N Numbers k such that k and k^2 use only the digits 0, 1, 5, 7 and 8.

%C Generated with DrScheme.

%H Jonathan Wellons, <a href="/A136872/b136872.txt">Table of n, a(n) for n = 1..142</a>

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

%e 870517087810501^2 = 757800000170075508718085871001.

%t With[{c={0,1,5,7,8}},Select[FromDigits/@Tuples[c,11],SubsetQ[c, IntegerDigits[ #^2]]&]] (* _Harvey P. Dale_, Sep 13 2019 *)

%K base,nonn

%O 1,3

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

%E More terms from _Harvey P. Dale_, Sep 13 2019