A220724 Number of ways to reciprocally link elements of an n X 7 array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors.

1, 717, 114900, 21914482, 4067687187, 759141297226, 141539684300104, 26392338517041335, 4921196474806555320, 917624537292862421240, 171103547699638196272026, 31904579896557581955181967

Offset

1,2

Comments

Column 7 of A220725.

Links

R. H. Hardin, Table of n, a(n) for n = 1..151

Example

Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
.00.67.47.00.00.79.00...00.67.49.00.67.46.47...00.67.47.69.46.46.47
.36.34.67.49.37.79.17...36.46.47.13.00.39.00...39.37.00.00.17.36.47
.00.36.46.34.13.36.14...00.36.46.46.46.46.14...36.14.00.36.46.34.00

Crossrefs

Cf. A220725.

Sequence in context: A151631 A183841 A332171 * A034587 A111416 A252528

Adjacent sequences: A220721 A220722 A220723 * A220725 A220726 A220727

Keyword

nonn

Author

R. H. Hardin, Dec 18 2012

Status

approved