A140662 - OEIS

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A140662

Number of possible column states for self-avoiding polygons in a slit of width n.

1, 3, 8, 20, 50, 126, 322, 834, 2187, 5797, 15510, 41834, 113633, 310571, 853466, 2356778, 6536381, 18199283, 50852018, 142547558, 400763222, 1129760414, 3192727796, 9043402500, 25669818475, 73007772801, 208023278208 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`Essentially equal to A001006(n+2)-1, n>1.`
	LINKS	`J. Alvarez, E.J. Janse van Rensburg et al. Self-avoiding walks and polygons in slits.`
	FORMULA	`a(n)=sum_{m=1..[(n+1)/2]} (n+1)!/((n+1-2m)!m!(m+1)!).`
	CROSSREFS	`Cf. A055151, A080159, A088617, A107131, A097610.` `Sequence in context: A026582 A187003 A101893 * A174198 A077997 A027220` `Adjacent sequences: A140659 A140660 A140661 * A140663 A140664 A140665`
	KEYWORD	`easy,nonn`
	AUTHOR	`R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 11 2008`

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Last modified February 15 12:25 EST 2012. Contains 205786 sequences.