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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.
0
1, 1, 2, 2, 10, 20, 248, 1072, 31178, 270026, 18806964, 329412610, 54393195014, 1931171930256, 749416883107560, 54217060622200086
OFFSET
0,3
FORMULA
a(n) = A340043(n, A002620(n-1)).
EXAMPLE
3 X 3 square cells
*---*---*---E
| | | |
*---*---*---*
| | | |
*---*---*---*
| | | |
S---*---*---*
a(3) = 2;
E E
| |
* *---*
| |
*---* * *---*
| | | |
S---* *---* S---*---*---*
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Seiichi Manyama, Dec 09 2022
STATUS
approved