A209626 Meandric numbers for a river crossing up to 11 parallel roads at n points.

1, 1, 2, 4, 10, 23, 63, 155, 448, 1152, 3452, 9158, 28177, 76537, 240343, 665073, 2122968, 5963685, 19295541, 54883588, 179608831, 516272903, 1706070421, 4948280698, 16490889347, 48203859456, 161842379157, 476304741819, 1609703418480, 4765887074059, 16201200791291

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 11 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..40

Crossrefs

Column k=11 of A380367.

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: A209383 A209621 A209622 * A209656 A209657 A209660

Adjacent sequences: A209623 A209624 A209625 * A209627 A209628 A209629

Keyword

nonn,changed

Author

Robert Price, May 07 2012

Extensions

a(21) onwards from Andrew Howroyd, Jan 31 2025

Status

approved