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Numbers k such that k and k^2 use only the digits 0, 3, 6, 7 and 9.
1

%I #9 Apr 12 2024 09:51:27

%S 0,3,6,30,60,63,300,306,600,603,630,3000,3006,3060,6000,6003,6030,

%T 6300,30000,30006,30060,30600,60000,60003,60030,60300,63000,63037,

%U 79603,300000,300006,300060,300600,306000,600000,600003,600030,600300,603000,630000,630370,796030,796076,3000000,3000006,3000060,3000600,3006000,3060000,6000000,6000003

%N Numbers k such that k and k^2 use only the digits 0, 3, 6, 7 and 9.

%C Generated with DrScheme.

%H Jonathan Wellons, <a href="/A136944/b136944.txt">Table of n, a(n) for n = 1..753</a>

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

%e 969067076796376^2 = 939090999330673300067366733376.

%t With[{ss={0,3,6,7,9}},Select[FromDigits/@Tuples[ss,7], SubsetQ[ ss, IntegerDigits[ #^2]]&]] (* _Harvey P. Dale_, May 29 2016 *)

%K base,nonn

%O 1,2

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