A209707 Meandric numbers for a river crossing up to 15 parallel roads at n points.

1, 1, 2, 4, 10, 23, 63, 155, 448, 1152, 3452, 9158, 28178, 76539, 240370, 665129, 2123438, 5964689, 19302281, 54898345, 179695808, 516467363, 1707124038, 4950679082, 16503152306, 48232213024, 161981435856, 476630676669, 1611253336964, 4769563838975, 16218280461398

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 15 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=15 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: A209656 A209657 A209660 * A210344 A210478 A210567

Adjacent sequences: A209704 A209705 A209706 * A209708 A209709 A209710

Keyword

nonn

Author

Robert Price, May 07 2012

Extensions

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

Status

approved