A333323 Number of self-avoiding closed paths on an n X n grid which pass through NW and SE corners.

1, 3, 42, 1799, 232094, 92617031, 115156685746, 442641690778179, 5224287477491915786, 188825256606226776728029, 20879416139356164466643759334, 7057757437924198729598570424130207, 7287699030020917172151307665469211016474, 22973720258279267139936821063450448822110219653

Offset: 2

Author

Seiichi Manyama, Mar 23 2020

Keywords

• nonn

Examples

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

Links

• Anthony J. Guttmann and Iwan Jensen, Table of n, a(n) for n = 2..27
• Anthony J. Guttmann and Iwan Jensen, Self-avoiding walks and polygons crossing a domain on the square and hexagonal lattices, arXiv:2208.06744 [math-ph], Aug 13 2022, Table D2 (with offset 1).
• Anthony J. Guttmann and Iwan Jensen, The gerrymander sequence, or A348456, arXiv:2211.14482 [math.CO], 2022.

Crossrefs

Cf. A007764, A333246, A333247, A333466.

Cf. A121785, A356610-A356616, A354511.

Programs

Python

# Using graphillion
from graphillion import GraphSet
import graphillion.tutorial as tl
def A333323(n):
    universe = tl.grid(n - 1, n - 1)
    GraphSet.set_universe(universe)
    cycles = GraphSet.cycles().including(1).including(n * n)
    return cycles.len()
print([A333323(n) for n in range(2, 10)])

Extensions

a(11) from Seiichi Manyama, Apr 07 2020

a(10) and a(12)-a(15) from Vaclav Kotesovec, Aug 16 2022 (computed by Anthony Guttmann)