1,2

G. C. Greubel, Table of n, a(n) for n = 1..10000

a(n) = n if and only if n is a prime.

a[ n_] := EulerPhi @ n - MoebiusMu @ n; Table[a[n], {n, 70}] (* Michael Somos, Jul 19 2011 *)

(PARI) {a(n) = if( n==0, 0, eulerphi( n) - moebius( n))} /* Michael Somos, Jul 19 2011 */

(MAGMA) [EulerPhi(n) - MoebiusMu(n): n in [1..100]]; // G. C. Greubel, Sep 03 2018

Cf. A000010, A008683.

Sequence in context: A332424 A293212 A157449 * A127705 A124386 A098668

Adjacent sequences: A053136 A053137 A053138 * A053140 A053141 A053142

nonn

N. J. A. Sloane, Mar 25 2000

approved