A209657 Meandric numbers for a river crossing up to 13 parallel roads at n points.

1, 1, 2, 4, 10, 23, 63, 155, 448, 1152, 3452, 9158, 28178, 76539, 240369, 665127, 2123408, 5964627, 19301713, 54897139, 179687084

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 13 parallel East-West roads n times.

Sequence derived from list of solutions described in A206432.

Links

Table of n, a(n) for n=0..20.

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: A209622 A209626 A209656 * A209660 A209707 A210344

Adjacent sequences: A209654 A209655 A209656 * A209658 A209659 A209660

Keyword

nonn,more

Author

Robert Price, May 07 2012

Status

approved