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A076686
a(n) = min(core(n),phi(n)) where core(n) is the squarefree part of n.
2
1, 1, 2, 1, 4, 2, 6, 2, 1, 4, 10, 3, 12, 6, 8, 1, 16, 2, 18, 5, 12, 10, 22, 6, 1, 12, 3, 7, 28, 8, 30, 2, 20, 16, 24, 1, 36, 18, 24, 10, 40, 12, 42, 11, 5, 22, 46, 3, 1, 2, 32, 13, 52, 6, 40, 14, 36, 28, 58, 15, 60, 30, 7, 1, 48, 20, 66, 17, 44, 24, 70, 2, 72, 36, 3, 19, 60, 24, 78, 5
OFFSET
1,3
LINKS
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