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A137007
Numbers k such that k and k^2 use only the digits 1, 2, 5 and 7.
1
1, 5, 11, 15, 715
OFFSET
1,2
COMMENTS
Generated with DrScheme.
No additional terms up to and including 7,777,777,777. - Harvey P. Dale, Sep 04 2018
No additional terms up to 10^26. - L. Joris Perrenet, Jul 02 2020
No additional terms up to 10^39. - Michael S. Branicky, Apr 12 2024
LINKS
EXAMPLE
715^2 = 511225.
MATHEMATICA
Module[{nn=10, c={1, 2, 5, 7}}, Select[Flatten[Table[FromDigits/@Tuples[c, n], {n, nn}]], SubsetQ[c, IntegerDigits[#^2]]&]] (* Harvey P. Dale, Sep 04 2018 *)
CROSSREFS
Sequence in context: A221743 A137008 A137010 * A137012 A259067 A314080
KEYWORD
base,nonn,more
AUTHOR
Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
STATUS
approved