A086031 - OEIS

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A086031

Number of nonisomorphic ways a loop can cross two parallel roads 2n times.

1, 1, 3, 7, 37, 207, 1470, 11169, 91166, 776841, 6865598, 62443973 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`0,3`
	COMMENTS	`There is no obligation to cross the lower road (cf. A077054).`
	LINKS	`Table of n, a(n) for n=0..11.`
	CROSSREFS	`Cf. A077054. Isomorphism classes from A085973.` `Sequence in context: A087208 A161675 A208809 * A174734 A152560 A162926` `Adjacent sequences: A086028 A086029 A086030 * A086032 A086033 A086034`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane and Jon Wild, Aug 25 2003`
	STATUS	`approved`

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Last modified November 15 09:02 EST 2017. Contains 294710 sequences.