%I #12 Sep 03 2020 06:41:50
%S 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,
%T 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,
%U 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
%N a(n) = min(core(n),phi(n)) where core(n) is the squarefree part of n.
%H Amiram Eldar, <a href="/A076686/b076686.txt">Table of n, a(n) for n = 1..10000</a>
%F Sum_{k=1..n} a(k) is asymptotic to c*n^2 with c = 0.239......
%t core[n_] := Times @@ (First[#]^Mod[Last[#], 2]& /@ FactorInteger[n]); a[n_] := Min[EulerPhi[n], core[n]]; Array[a, 80] (* _Amiram Eldar_, Sep 03 2020 *)
%o (PARI) a(n)=min(core(n),eulerphi(n))
%Y Cf. A000010, A007913, A076685.
%K nonn
%O 1,3
%A _Benoit Cloitre_, Oct 25 2002