A077550 - OEIS

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A077550

Number of nonisomorphic ways a river (or undirected line) can cross two perpendicular roads n times (orbits of A076875 under symmetry group of order 8).

1, 1, 2, 3, 9, 21, 54, 131 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`0,3`
	COMMENTS	`There is no constraint on touching any particular sector.`
	LINKS	`Table of n, a(n) for n=0..7.`
	CROSSREFS	`Cf. A076875 (total number of solutions), A076906, A076907 (if line is directed)` `Sequence in context: A015951 A101531 A099607 * A056780 A141505 A111360` `Adjacent sequences: A077547 A077548 A077549 * A077551 A077552 A077553`
	KEYWORD	`nonn`
	AUTHOR	`N. J. A. Sloane and Jon Wild, Aug 25 2003`
	STATUS	`approved`

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Last modified May 18 23:01 EDT 2013. Contains 225428 sequences.