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A137078
Numbers k such that k and k^2 use only the digits 2, 3, 4 and 9.
0
2, 3, 4943, 499423, 49993443, 4999932923, 499999999293429243923, 499999999999293429243923
OFFSET
1,1
COMMENTS
Generated with DrScheme.
LINKS
EXAMPLE
4999932923^2 = 24999329234499323929.
MAPLE
g:= n -> convert(convert(n, base, 10), set) subset {2, 3, 4, 9}:
Res:= 2, 3:
extend:= proc(n, d) local B; global Res;
B:= {seq(x*10^d+n, x=[2, 3, 4, 9])};
Res:= Res, op(select(t -> g(t^2), B));
op(select(t -> g(t^2 mod 10^(d+1)), B))
end proc:
Agenda:= {2, 3, 4, 9}:
for d from 1 to 25 do Agenda:= map(extend, Agenda, d) od:
sort([Res]); # Robert Israel, Oct 29 2018
CROSSREFS
Cf. A136809.
Sequence in context: A271631 A068826 A085944 * A146026 A115640 A212494
KEYWORD
base,nonn,more
AUTHOR
Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
EXTENSIONS
a(7)-a(8) from Andrew Howroyd, Oct 24 2018
STATUS
approved