A333247 Number of self-avoiding closed paths on an n X n grid which pass through NW and SW corners.

1, 4, 47, 1843, 232905, 92729439, 115234959344, 442748883422394

Offset

2,2

Comments

a(11) = 188829168009674568016545. - Seiichi Manyama, Apr 07 2020

Links

Table of n, a(n) for n=2..9.

Example

a(2) = 1;
   +--*
   |  |
   +--*
a(3) = 4;
   +--*--*   +--*--*   +--*      +--*
   |     |   |     |   |  |      |  |
   *     *   *  *--*   *  *--*   *  *
   |     |   |  |      |     |   |  |
   +--*--*   +--*      +--*--*   +--*

Prog

(Python)
# Using graphillion
from graphillion import GraphSet
import graphillion.tutorial as tl
def A333247(n):
    universe = tl.grid(n - 1, n - 1)
    GraphSet.set_universe(universe)
    cycles = GraphSet.cycles().including(1).including(n)
    return cycles.len()
print([A333247(n) for n in range(2, 10)])

Crossrefs

Cf. A271507, A333246, A333323, A333466.

Sequence in context: A251665 A210828 A361560 * A330039 A141040 A182102

Adjacent sequences: A333244 A333245 A333246 * A333248 A333249 A333250

Keyword

nonn,more

Author

Seiichi Manyama, Mar 23 2020

Status

approved