id:A082936 - OEIS Search Results

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(1/(3*n))*Sum_{d|n, d even} phi(2*n/d)*binomial(3d/2,d).

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1, 3, 10, 43, 201, 1038, 5538, 30667, 173593, 1001603, 5864750, 34769374, 208267320, 1258579654, 7663720710, 46976034379, 289628805623, 1794932468571, 11175157356522, 69864075597643, 438403736549145, 2760351032959050, 17433869214973754, 110420300879752990 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`a(n) = number of necklaces of n white beads and 2n black beads. - David Callan (callan(AT)stat.wisc.edu), Mar 28 2004`
	LINKS	`M. Bousquet and C. Lamathe, Enumeration of solid trees according to edge number and edge degree distribution, Discr. Math., 298 (2005), 115-141.`
	MAPLE	`with(numtheory): f := proc(n) local t1, d; t1 := 0; for d from 1 to n do if n mod d = 0 then if d mod 2 = 0 then t1 := t1+phi(n/d)binomial(3d/2, d) fi; fi; od; 2t1/(3n); end; # use with n even`
	CROSSREFS	`Sequence in context: A042545 A151084 A151085 this_sequence A030935 A132428 A030890` `Adjacent sequences: A082933 A082934 A082935 this_sequence A082937 A082938 A082939`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), May 26 2003`

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Last modified November 25 08:46 EST 2009. Contains 167481 sequences.

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