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A208452
Meandric numbers for a river crossing up to 6 parallel roads at n points.
18
1, 1, 2, 4, 10, 23, 63, 154, 446, 1135, 3416, 8947, 27712, 74204, 235041, 640552, 2065849, 5711840, 18696838, 52321747, 173413647, 490279035, 1642287831, 4684178185, 15834649146, 45511151647, 155077912223, 448722569787, 1539743907074, 4481866870316, 15474663284941
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 6 parallel East-West roads n times.
Sequence derived from list of solutions described in A206432.
LINKS
CROSSREFS
Cf. A005316 (sequence for one road; extensive references and links).
Cf. A076876 (sequence for two parallel roads).
Cf. A206432 (sequence for unlimited number of parallel roads).
Sequence in context: A205999 A208126 A370646 * A208453 A209383 A209621
KEYWORD
nonn
AUTHOR
Robert Price, May 07 2012
EXTENSIONS
a(21)-a(36) from Andrew Howroyd, Dec 05 2015
STATUS
approved