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Meandric numbers for a river crossing up to 8 parallel roads at n points.
18

%I #21 Oct 26 2024 04:07:55

%S 1,1,2,4,10,23,63,155,448,1151,3450,9137,28134,76236,239712,661374,

%T 2115046,5921549,19203568,54422726,178585838,511343777,1694965469,

%U 4896195579,16371992897,47656781437,160578870274,470571482142,1596323368095,4705798878362,16059653893209

%N Meandric numbers for a river crossing up to 8 parallel roads at n points.

%C Number of ways that a river (or directed line) that starts in the South and flows East can cross up to 8 parallel East-West roads n times.

%C Sequence derived from list of solutions described in A206432.

%H Andrew Howroyd, <a href="/A209383/b209383.txt">Table of n, a(n) for n = 0..36</a>

%Y Cf. A005316 (sequence for one road; extensive references and links).

%Y Cf. A076876 (sequence for two parallel roads).

%Y 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).

%Y Cf. A206432 (sequence for unlimited number of parallel roads).

%Y Cf. A076875, A076906, A076907.

%K nonn

%O 0,3

%A _Robert Price_, May 07 2012

%E a(21)-a(36) from _Andrew Howroyd_, Dec 05 2015