A208062 Meandric numbers for a river crossing up to 4 parallel roads at n points.

1, 1, 2, 4, 10, 22, 61, 142, 420, 1017, 3146, 7844, 25083, 63974, 209875, 545060, 1824949, 4810138, 16374993, 43695535, 150820899, 406669871, 1420155120, 3863613980, 13627843933, 37363313071, 132933980698, 366939582498, 1315436809855, 3652777067949, 13182411646150

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 4 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: A205499 A148086 A005962 * A179468 A203254 A076875

Adjacent sequences: A208059 A208060 A208061 * A208063 A208064 A208065

Keyword

nonn

Author

Robert Price, May 07 2012

Extensions

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

Status

approved