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A080736 Multiplicative function defined by a(1)=1, a(2)=0, a(2^r) = phi(2^r) (r>1), a(p^r) = phi(p^r) (p odd prime, r>=1), where phi is Euler's function A000010. 3
1, 0, 2, 2, 4, 0, 6, 4, 6, 0, 10, 4, 12, 0, 8, 8, 16, 0, 18, 8, 12, 0, 22, 8, 20, 0, 18, 12, 28, 0, 30, 16, 20, 0, 24, 12, 36, 0, 24, 16, 40, 0, 42, 20, 24, 0, 46, 16, 42, 0, 32, 24, 52, 0, 40, 24, 36, 0, 58, 16, 60, 0, 36, 32, 48, 0, 66, 32, 44, 0, 70, 24, 72, 0, 40, 36, 60, 0, 78, 32 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(A016825(n)) = 0; a(A000040(n)) = A000040(n) - 1. - Reinhard Zumkeller, Jun 11 2012

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = if n mod 4 = 2 then 0 else A000010(n). - Reinhard Zumkeller, Jun 13 2012

PROG

(PARI) {for(n=1, 81, f=factor(n); print1(if(n==1, 1, if(f[1, 1]==2&&f[1, 2]==1, 0, prod(j=1, matsize(f)[1], eulerphi(f[j, 1]^f[j, 2])))), ", "))}

(Haskell)

a080736 n = if n `mod` 4 == 2 then 0 else a000010 n

-- Reinhard Zumkeller, Jun 13 2012, Jun 11 2012

CROSSREFS

Cf. A080737.

Cf. A000010, A141809.

Sequence in context: A127786 A030207 A061006 * A276151 A144412 A240491

Adjacent sequences:  A080733 A080734 A080735 * A080737 A080738 A080739

KEYWORD

nonn,easy,mult

AUTHOR

N. J. A. Sloane, Mar 08 2003

EXTENSIONS

More terms and PARI code from Klaus Brockhaus, Mar 10 2003

STATUS

approved

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Last modified September 18 13:06 EDT 2018. Contains 315130 sequences. (Running on oeis4.)