A323141 Number of self-trapped uncrossed king's paths on an infinite board after n steps, reduced for symmetry.

0, 0, 0, 0, 2, 19, 150, 1043, 6843, 43192, 266529, 1619983, 9746883, 58220994, 345919915

Offset

1,5

Links

Table of n, a(n) for n=1..15.

Example

a(5) = 2: There are 2 walks where the king is blocked after 5 steps, because for the diagonal moves it would have to cross its previous path.
.
  o       2       o       o       3        o
        /   \                   /   \
      /       \               /        \
    /           \           /            \
  3       5       1       4 - - - 5        2
  |     /       /                        /
  |   /       /                        /
  | /       /                        /
  4       S       o       S - - -  1       o

Crossrefs

Cf. A003192, A077482, A272773, A323140.

Sequence in context: A220792 A220957 A280546 * A319962 A161608 A037748

Adjacent sequences: A323138 A323139 A323140 * A323142 A323143 A323144

Keyword

nonn,more,hard

Author

Hugo Pfoertner, Jan 05 2019

Status

approved