id:A128656 - OEIS Search Results

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Number of polygons on n vertices with four faces such that the source of the polygon lies on exactly two faces.

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1

2, 8, 44, 240, 1248, 6224, 30052, 141536, 653744, 2973072, 13351192, 59333408, 261378944, 1142885664, 4965331028, 21452209600, 92230169232, 394819386896, 1683663903016, 7155148746912, 30313584232640, 128067598573408 (list; graph; listen)

	OFFSET	`1,1`
	LINKS	`T. Mansour and S. Severini, Grid polygons from permutations and their enumeration by the kernel method`
	FORMULA	`a(n) = 2(n+2) * 4^(n-3) - 2(n+1) C(2*n-4,n-3).`
	CROSSREFS	`Sequence in context: A075817 A018985 A018986 this_sequence A047851 A121747 A014508` `Adjacent sequences: A128653 A128654 A128655 this_sequence A128657 A128658 A128659`
	KEYWORD	`nonn`
	AUTHOR	`Ralf Stephan, May 08 2007`

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.

AT&T Labs Research