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A136996
Numbers k such that k and k^2 use only the digits 1, 2, 4 and 7.
0
1, 2, 11, 12, 21, 421, 1214171, 2777177421
OFFSET
1,2
COMMENTS
Generated with DrScheme.
LINKS
EXAMPLE
2777177421^2 = 7712714427712211241.
MATHEMATICA
Module[{c = {1, 2, 4, 7}}, Select[Flatten[Table[FromDigits /@ Tuples[c, n], {n, 10}]], SubsetQ[c, IntegerDigits[#^2]] &]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 02 2017 *)
CROSSREFS
Sequence in context: A136967 A213975 A137001 * A238109 A374596 A113720
KEYWORD
base,nonn,more
AUTHOR
Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
STATUS
approved