login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Numbers k such that k and k^2 use only the digits 0, 4, 6, 7 and 9.
1

%I #10 Apr 12 2024 09:51:27

%S 0,7,64,70,97,640,700,970,997,6400,6907,7000,7064,9700,9970,9997,

%T 64000,69070,70000,70640,77974,97000,99700,99747,99970,99997,640000,

%U 666907,667907,690700,700000,700497,706400,774647,777676,779740,970000,997000,997470,999700,999747,999970,999997,6400000,6400774,6669070,6679070,6907000,7000000

%N Numbers k such that k and k^2 use only the digits 0, 4, 6, 7 and 9.

%C Generated with DrScheme.

%H Jonathan Wellons, <a href="/A136955/b136955.txt">Table of n, a(n) for n = 1..714</a>

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

%e 700709640764747^2 = 490994000660660790706997974009.

%t With[{c={0,4,6,7,9}},Select[FromDigits/@Tuples[c,7],SubsetQ[ c,IntegerDigits[ #^2]]&]] (* _Harvey P. Dale_, Oct 11 2020 *)

%K base,nonn

%O 1,2

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