A011797 - OEIS

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A011797

[ C(n,6)/7 ].

0, 0, 0, 0, 0, 0, 0, 1, 4, 12, 30, 66, 132, 245, 429, 715, 1144, 1768, 2652, 3876, 5537, 7752, 10659, 14421, 19228, 25300, 32890, 42287, 53820, 67860, 84825, 105183, 129456, 158224, 192129, 231880, 278256 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,9`
	COMMENTS	`a(n-1)=number of aperiodic necklaces (Lyndon words) with 7 black beads and n-7 white beads.`
	LINKS	`D. J. Broadhurst, On the enumeration of irreducible k-fold Euler sums and their roles in knot theory and field theory` `Index entries for sequences related to Lyndon words`
	FORMULA	`G.f.: (1+x^3)^2/((1-x)^4(1-x^2)^2(1-x^7)).` `a(n) = floor(binomial(n+1,7)/(n+1)). [From Gary Detlefs, Nov 23 2011]`
	CROSSREFS	`Cf. A000031, A001037, A051168. Same as A051172(n+1).` `First differences of A011853.` `A column of triangle A011847.` `Sequence in context: A166213 A004036 A051172 * A032192 A118425 A097809` `Adjacent sequences: A011794 A011795 A011796 * A011798 A011799 A011800`
	KEYWORD	`nonn,easy`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com), David Broadhurst (D.Broadhurst(AT)open.ac.uk)`

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Last modified February 17 19:13 EST 2012. Contains 206085 sequences.