A220731 Number of ways to reciprocally link elements of an 7Xn array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors

1, 64, 9667, 3751888, 1208447287, 418227762771, 141539684300104, 48392485908572308

Offset

1,2

Comments

Row 7 of A220725

Links

Table of n, a(n) for n=1..8.

Example

Some solutions for n=3 0=self 1=nw 3=ne 4=w 6=e 7=sw 9=se (reciprocal directions total 10)
.69.47.00...00.00.00...69.49.00...00.67.47...69.49.00...00.69.47...00.00.00
.36.14.00...00.79.00...00.16.14...39.36.47...00.17.17...69.34.17...00.79.00
.69.47.00...36.46.14...69.46.47...00.13.00...36.34.00...00.13.00...36.49.17
.39.17.00...00.00.00...00.13.00...00.00.00...69.49.00...00.67.47...00.36.14
.36.14.00...00.00.00...00.79.00...00.79.00...00.17.17...39.37.00...00.79.00
.00.67.47...69.49.00...39.67.14...36.46.14...39.37.00...39.19.00...39.67.14
.36.34.00...00.16.14...36.14.00...00.00.00...36.14.00...00.16.14...36.14.00

Crossrefs

Sequence in context: A222140 A093264 A264146 * A239403 A254607 A236690

Adjacent sequences: A220728 A220729 A220730 * A220732 A220733 A220734

Keyword

nonn

Author

R. H. Hardin Dec 18 2012

Status

approved