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A053139 phi(n) - mu(n). 0
0, 2, 3, 2, 5, 1, 7, 4, 6, 3, 11, 4, 13, 5, 7, 8, 17, 6, 19, 8, 11, 9, 23, 8, 20, 11, 18, 12, 29, 9, 31, 16, 19, 15, 23, 12, 37, 17, 23, 16, 41, 13, 43, 20, 24, 21, 47, 16, 42, 20, 31, 24, 53, 18, 39, 24, 35, 27, 59, 16, 61, 29, 36, 32, 47, 21, 67, 32 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

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

MATHEMATICA

a[ n_] := EulerPhi @ n - MoebiusMu @ n (* Michael Somos Jul 19 2011 *)

PROG

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

CROSSREFS

Cf. A000010, A008683.

Sequence in context: A164880 A157449 A127705 * A124386 A098668 A112763

Adjacent sequences:  A053136 A053137 A053138 * A053140 A053141 A053142

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Mar 25 2000

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Last modified February 16 21:51 EST 2012. Contains 205978 sequences.