A358996 Number of self-avoiding paths of length 2*(n+A002620(n-1)) along the edges of a grid with n X n square cells, which do not pass above the diagonal, start at the lower left corner and finish at the upper right corner.

1, 1, 2, 2, 10, 20, 248, 1072, 31178, 270026, 18806964, 329412610, 54393195014, 1931171930256, 749416883107560, 54217060622200086

Offset

0,3

Links

Table of n, a(n) for n=0..15.

Formula

a(n) = A340043(n, A002620(n-1)).

Example

3 X 3 square cells
  *---*---*---E
  |   |   |   |
  *---*---*---*
  |   |   |   |
  *---*---*---*
  |   |   |   |
  S---*---*---*
a(3) = 2;
              E              E
              |              |
              *          *---*
              |          |
      *---*   *          *---*
      |   |   |              |
  S---*   *---*  S---*---*---*

Crossrefs

Cf. A000108, A002620, A340005, A340043.

Sequence in context: A348957 A303565 A291856 * A192309 A151456 A336490

Adjacent sequences: A358993 A358994 A358995 * A358997 A358998 A358999

Keyword

nonn,more

Author

Seiichi Manyama, Dec 09 2022

Status

approved