A085919 - OEIS

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A085919

Number of ways a loop can cross three roads meeting in a Y n times.

3, 0, 3, 1, 9, 6, 45, 42, 279, 320, 1977, 2610, 15306, 22404, 126300, 200158, 1093515, 1846314, 9830547, 17481864 (list; graph; refs; listen; history; internal format)

	OFFSET	`0,1`
	COMMENTS	`The Mercedes-Benz problem: closed meanders crossing a Y.`
	LINKS	`Anonymous, Illustration for a(3) = 1`
	EXAMPLE	`With three crossings the loop must cut each road exactly once, so a(3) = 1.`
	CROSSREFS	`Similar to A078104, but without the constraint of touching the (-, -) quadrant.` `Sequence in context: A127372 A051171 A166445 * A105824 A171911 A180193` `Adjacent sequences: A085916 A085917 A085918 * A085920 A085921 A085922`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane (njas(AT)research.att.com) and Jon Wild (wild(AT)music.mcgill.ca), Aug 25 2003`

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Last modified February 15 21:56 EST 2012. Contains 205860 sequences.