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A323700
Number of rooted uncrossed knight's walks on an infinite chessboard trapped after n moves with first move specified.
1
1, 8, 56, 406, 2572, 16596, 102654, 642441, 3914084
OFFSET
4,2
COMMENTS
Trapping occurs if the walk cannot be continued without reusing an already visited field or creating an intersection of the path segments formed by straight lines connecting consecutively visited fields.
The shortest self-trapped walk has 4 moves, i.e., a(n)=0 for n < 4.
EXAMPLE
a(4) = 1 because there is only one trapped walk of 4 moves, written in algebraic chess notation: (N) b1 d2 b3 a1 c2.
For longer walks see link to illustrations in A323699.
CROSSREFS
KEYWORD
nonn,walk,more,hard
AUTHOR
Hugo Pfoertner, Jan 24 2019
STATUS
approved