id:A109007 - OEIS Search Results

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GCD(n,3).

+0
7

3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1 (list; graph; listen)

	OFFSET	`0,1`
	COMMENT	`For n>1: a(n) = GCD of the n-th and (n+2)-th triangular numbers = A050873(A000217(n+2),A000217(n)). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), May 28 2007`
	FORMULA	`a(n) = 1 + 2[3\|n] = 1 + 2(1 + 2cos(2nPi/3])/3, where [x\|y] = 1 when x divides y, 0 otherwise.` `a(n) = a(n-3).` `Multiplicative with a(p^e, 3) = GCD(p^e, 3). David W. Wilson (davidwwilson(AT)comcast.net) Jun 12, 2005.` `O.g.f.: -(3+x+x^2)/((x-1)*(x^2+x+1)) . - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 24 2007`
	CROSSREFS	`Cf. A109004.` `Cf. A026741, A130334.` `Sequence in context: A098094 A087283 A111625 this_sequence A132951 A101685 A049653` `Adjacent sequences: A109004 A109005 A109006 this_sequence A109008 A109009 A109010`
	KEYWORD	`nonn,easy,mult`
	AUTHOR	`Mitch Harris (Harris.Mitchell(AT)mgh.harvard.edu)`

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Last modified July 26 23:19 EDT 2008. Contains 142293 sequences.

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