A208452 Meandric numbers for a river crossing up to 6 parallel roads at n points.

1, 1, 2, 4, 10, 23, 63, 154, 446, 1135, 3416, 8947, 27712, 74204, 235041, 640552, 2065849, 5711840, 18696838, 52321747, 173413647, 490279035, 1642287831, 4684178185, 15834649146, 45511151647, 155077912223, 448722569787, 1539743907074, 4481866870316, 15474663284941

Offset

0,3

Comments

Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 6 parallel East-West roads n times.

Sequence derived from list of solutions described in A206432.

Links

Andrew Howroyd, Table of n, a(n) for n = 0..36

Crossrefs

Cf. A005316 (sequence for one road; extensive references and links).

Cf. A076876 (sequence for two parallel roads).

Cf. A204352, A208062, A208126, A208452, A208453, A209383, A209621, A209622, A209626, A209656, A209657, A209660, A209707, A210344, A210478, A210567, A210592 (sequences for 3 to 19 parallel roads).

Cf. A206432 (sequence for unlimited number of parallel roads).

Cf. A076875, A076906, A076907.

Sequence in context: A205999 A208126 A370646 * A208453 A209383 A209621

Adjacent sequences: A208449 A208450 A208451 * A208453 A208454 A208455

Keyword

nonn

Author

Robert Price, May 07 2012

Extensions

a(21)-a(36) from Andrew Howroyd, Dec 05 2015

Status

approved