|
| |
|
|
A206432
|
|
Meandric numbers for a river crossing any number of parallel roads at n points.
|
|
17
|
|
|
|
1, 1, 2, 4, 10, 23, 63, 155, 448, 1152, 3452, 9158, 28178, 76539, 240370, 665129, 2123439, 5964691, 19302316, 54898417, 179696559
(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 any number of parallel East-West roads n times.
Of course, the number of roads crossed cannot be more than the number of crossings, n.
A file (28GB) listing all solutions through n=20 is available from the author.
|
|
|
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. A076875, A076906, A076907.
Sequence in context: A210478 A210567 A210592 * A124480 A130967 A148087
Adjacent sequences: A206429 A206430 A206431 * A206433 A206434 A206435
|
|
|
KEYWORD
|
nonn,more,nice
|
|
|
AUTHOR
|
Robert Price, May 07 2012
|
|
|
STATUS
|
approved
|
| |
|
|
