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A078461 a(n) = 0 if n is divisible by the square of odd prime, a(n) = 1 if n is an odd squarefree number, a(n) = 2 otherwise. 1
1, 2, 1, 2, 1, 2, 1, 2, 0, 2, 1, 2, 1, 2, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 0, 2, 0, 2, 1, 2, 1, 2, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1, 2, 0, 2, 1, 2, 0, 0, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1, 2, 0, 2, 1, 2, 1, 2, 1, 2, 1, 0, 1, 2, 0, 2, 1, 2, 1, 2, 0, 2, 1, 2, 1, 2, 1, 2, 1, 0, 1, 2, 1, 2, 1, 2, 1, 0, 0, 0, 1, 2, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

FORMULA

Dirichlet g.f.: zeta(s)/zeta(2s)*2^s/(2^s-1). - Ralf Stephan, Jun 17 2007

Sum_{k=1..n} a(k) ~ 12*n / Pi^2. - Vaclav Kotesovec, Feb 02 2019

PROG

(PARI) a(n)=if(n<1, 0, direuler(p=2, n, if(p%2==1, 1+X, if(p%2, 1, (1+X)/(1-X))))[n])

(PARI) A078461(n) = (issquarefree(n/2^valuation(n, 2))*(2-(n%2))); \\ Antti Karttunen, Sep 27 2018

CROSSREFS

Cf. A038838, A056911.

Sequence in context: A062754 A045888 A107279 * A280535 A221171 A319610

Adjacent sequences:  A078458 A078459 A078460 * A078462 A078463 A078464

KEYWORD

mult,nonn

AUTHOR

Benoit Cloitre, Dec 31 2002

STATUS

approved

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Last modified November 16 17:04 EST 2019. Contains 329201 sequences. (Running on oeis4.)