id:A045947 - OEIS Search Results

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Triangles in open triangular matchstick arrangement (triangle minus one side) of side n.

+0
2

0, 0, 2, 7, 17, 33, 57, 90, 134, 190, 260, 345, 447, 567, 707, 868, 1052, 1260, 1494, 1755, 2045, 2365, 2717, 3102, 3522, 3978, 4472, 5005, 5579, 6195, 6855, 7560, 8312, 9112, 9962, 10863, 11817, 12825, 13889, 15010, 16190, 17430, 18732, 20097, 21527 (list; graph; listen)

	OFFSET	`0,3`
	FORMULA	`G.f.: (2x^2+x^3)/((1-x)^3(1-x^2)) - Michael Somos`
	PROGRAM	`(PARI) a(n)=(4n^3+2n^2-4*n)\16`
	CROSSREFS	`First differences of A082289.` `Sequence in context: A086513 A166381 A083723 this_sequence A145066 A014148 A070070` `Adjacent sequences: A045944 A045945 A045946 this_sequence A045948 A045949 A045950`
	KEYWORD	`nonn,easy,nice`
	AUTHOR	`R. K. Guy`

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Last modified November 25 14:49 EST 2009. Contains 167514 sequences.

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