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A351109 Number of simple paths for a Racetrack car (using von Neumann neighborhood) with initial velocity zero, going from one corner to the diagonally opposite corner on an n X n grid. 2
1, 0, 2, 8, 40, 1380, 211164, 205331148 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..8.

Wikipedia, Racetrack

EXAMPLE

For n = 4 the following paths, together with their reflections in the diagonal, exist. The numbers give the positions of the car after successive steps. In total, there are a(4) = 2*4 = 8 possible paths.

...3 ...4 ...4 ...5

.... ...3 ..3. ...4

..2. ..2. ..2. ...3

01.. 01.. 01.. 012.

CROSSREFS

Main diagonal of A351108.

Cf. A007764, A351042, A351107.

Sequence in context: A140363 A280921 A208962 * A012597 A012534 A092354

Adjacent sequences: A351106 A351107 A351108 * A351110 A351111 A351112

KEYWORD

nonn,more

AUTHOR

Pontus von Brömssen, Feb 01 2022

STATUS

approved

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Last modified December 8 22:05 EST 2022. Contains 358698 sequences. (Running on oeis4.)