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A318320 a(n) = (psi(n) - phi(n))/2. 6

%I

%S 0,1,1,2,1,5,1,4,3,7,1,10,1,9,8,8,1,15,1,14,10,13,1,20,5,15,9,18,1,32,

%T 1,16,14,19,12,30,1,21,16,28,1,42,1,26,24,25,1,40,7,35,20,30,1,45,16,

%U 36,22,31,1,64,1,33,30,32,18,62,1,38,26,60,1,60,1,39,40,42,18,72,1,56,27,43,1,84,22,45,32,52,1,96

%N a(n) = (psi(n) - phi(n))/2.

%H Antti Karttunen, <a href="/A318320/b318320.txt">Table of n, a(n) for n = 1..65537</a>

%F a(n) = (A001615(n) - A000010(n))/2 = A292786(n)/2.

%F a(n) = A291784(n) - A000010(n).

%F a(n) = A318326(n) + A318442(n).

%o (PARI) A318320(n) = sumdiv(n,d,(-1==moebius(n/d))*d);

%o (PARI) A318320(n) = ((n*sumdivmult(n, d, issquarefree(d)/d))-eulerphi(n))/2;

%Y Cf. A000010, A001615, A291784, A292786, A318325, A318326, A318442.

%Y Differs from A069359 for the first time at n=30, where a(30) = 32, while A069359(30) = 31.

%K nonn,look

%O 1,4

%A _Antti Karttunen_, Aug 26 2018

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Last modified November 13 02:59 EST 2019. Contains 329085 sequences. (Running on oeis4.)