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A137106
Numbers k such that k and k^2 use only the digits 2, 4, 7 and 8.
0
2, 22, 28, 88, 278, 472, 478, 2878
OFFSET
1,1
COMMENTS
Generated with DrScheme.
No further terms up to 20 billion. - Harvey P. Dale, Dec 15 2011
No further terms up to 10^15. - Travis Vasquez, Oct 23 2024
LINKS
EXAMPLE
2878^2 = 8282884.
MATHEMATICA
oksQ[n_]:=Module[{idn2=Union[IntegerDigits[n^2]]}, And@@Table[MemberQ[{2, 4, 7, 8}, idn2[[i]]], {i, Length[idn2]}]]; Select[FromDigits/@Flatten[ Table[ Tuples[ {2, 4, 7, 8}, n], {n, 9}], 1], oksQ] (* Harvey P. Dale, Dec 15 2011 *)
CROSSREFS
Sequence in context: A074160 A368406 A137074 * A053962 A111771 A052001
KEYWORD
base,nonn,more
AUTHOR
Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
STATUS
approved