A358996 - OEIS

%I #14 Dec 09 2022 16:05:13

%S 1,1,2,2,10,20,248,1072,31178,270026,18806964,329412610,54393195014,

%T 1931171930256,749416883107560,54217060622200086

%N 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.

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

%e 3 X 3 square cells

%e   *---*---*---E

%e   |   |   |   |

%e   *---*---*---*

%e   |   |   |   |

%e   *---*---*---*

%e   |   |   |   |

%e   S---*---*---*

%e a(3) = 2;

%e               E              E

%e               |              |

%e               *          *---*

%e               |          |

%e       *---*   *          *---*

%e       |   |   |              |

%e   S---*   *---*  S---*---*---*

%Y Cf. A000108, A002620, A340005, A340043.

%K nonn,more

%O 0,3

%A _Seiichi Manyama_, Dec 09 2022