A030435 - OEIS

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A030435

Expansion of (1+x-2*x^2-x^3)/(1/2-2*x^2+x^4).

2, 2, 4, 6, 12, 20, 40, 68, 136, 232, 464, 792, 1584, 2704, 5408, 9232, 18464, 31520, 63040, 107616, 215232, 367424, 734848, 1254464, 2508928, 4283008, 8566016, 14623104, 29246208, 49926400, 99852800 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,1`
	COMMENTS	`Also (starting 4,6,...) the number of zig-zag paths from top to bottom of a rectangle of width 7, whose color is that of the top right corner. [From Joseph Myers (jsm(AT)polyomino.org.uk), Dec 24 2008]`
	LINKS	`Joseph Myers, BMO 2008--2009 Round 1 Problem 1---Generalisation`
	CROSSREFS	`a(n)=2 A030436(n).` `Sequence in context: A037163 A059123 A001679 * A063886 A003000 A122536` `Adjacent sequences: A030432 A030433 A030434 * A030436 A030437 A030438`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com).`

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Last modified February 15 05:45 EST 2012. Contains 205694 sequences.