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A209656 Meandric numbers for a river crossing up to 12 parallel roads at n points. 20
1, 1, 2, 4, 10, 23, 63, 155, 448, 1152, 3452, 9158, 28178, 76538, 240368, 665100, 2123379, 5964156, 19301178, 54890366, 179679030 (list; graph; refs; listen; history; text; internal format)
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 12 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: A209621 A209622 A209626 * A209657 A209660 A209707

Adjacent sequences:  A209653 A209654 A209655 * A209657 A209658 A209659

KEYWORD

nonn,more

AUTHOR

Robert Price, May 07 2012

STATUS

approved

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Last modified January 25 16:01 EST 2022. Contains 350572 sequences. (Running on oeis4.)