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

Author

Seiichi Manyama, Mar 23 2020

Keywords

• nonn
• more

Comments

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

Examples

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

Crossrefs

Cf. A271507, A333246, A333323, A333466.

Programs

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)])