OFFSET
1,1
COMMENTS
Such an even number always exists.
LINKS
T. D. Noe, Table of n, a(n) for n=1..10000
Maxim Rytin, Finding the Inverse of Euler Totient Function (1999).
MAPLE
f:= proc(m) local L;
L:= numtheory:-invphi(m);
if L = [] then NULL
else min(select(type, L, even))
fi
end proc:
map(f, [1, seq(2*k, k=1..1000)]); # Robert Israel, Oct 07 2015
MATHEMATICA
f[m_] := Module[{L}, L = invphi[m]; If[L == {}, Nothing, Min[Select[L, EvenQ]]]];
f /@ Join [{1}, 2 Range[1000]] (* Jean-François Alcover, Aug 28 2020, using Maxim Rytin's invphi function *)
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Aug 14 2008
STATUS
approved