OFFSET
1,3
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
Sum_{k=1..n} a(k) is asymptotic to c*n^2 with c = 0.239......
MATHEMATICA
core[n_] := Times @@ (First[#]^Mod[Last[#], 2]& /@ FactorInteger[n]); a[n_] := Min[EulerPhi[n], core[n]]; Array[a, 80] (* Amiram Eldar, Sep 03 2020 *)
PROG
(PARI) a(n)=min(core(n), eulerphi(n))
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Oct 25 2002
STATUS
approved