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A109008 GCD(n,4). +0
4
4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 2, 1, 4 (list; graph; listen)
OFFSET

0,1

FORMULA

a(n) = 1 + [2|n] + 2*[4|n] = 2 + (-1)^n + cos(n*Pi/2), where [x|y] = 1 when x divides y, 0 otherwise.

a(n) = a(n-4).

Multiplicative with a(p^e, 4) = GCD(p^e, 4). David W. Wilson (davidwwilson(AT)comcast.net) Jun 12, 2005.

CROSSREFS

Cf. A109004.

Sequence in context: A010640 A087230 A030787 this_sequence A074695 A069098 A126241

Adjacent sequences: A109005 A109006 A109007 this_sequence A109009 A109010 A109011

KEYWORD

nonn,easy,mult

AUTHOR

Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu)

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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