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A085919
Number of ways a loop can cross three roads meeting in a Y n times.
1
3, 0, 3, 1, 9, 6, 45, 42, 279, 320, 1977, 2610, 15306, 22404, 126300, 200158, 1093515, 1846314, 9830547, 17481864
(list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
The Mercedes-Benz problem: closed meanders crossing a Y.
LINKS
Table of n, a(n) for n=0..19.
Anonymous, Illustration for a(3) = 1
EXAMPLE
With three crossings the loop must cut each road exactly once, so a(3) = 1.
CROSSREFS
Similar to A078104, but without the constraint of touching the (-, -) quadrant.
Sequence in context: A166445 A374139 A298082 * A352613 A105824 A171911
Adjacent sequences: A085916 A085917 A085918 * A085920 A085921 A085922
KEYWORD
nonn
AUTHOR
N. J. A. Sloane and Jon Wild, Aug 25 2003
STATUS
approved

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Last modified September 30 03:24 EDT 2024. Contains 376325 sequences.
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