A220680 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without consecutive collinear links.

1, 441, 22000, 2316754, 215926776, 21051034046, 2045717834201, 198460804181024, 19267871745544463, 1870273847823355410, 181541549823743511322, 17622155633363587138681, 1710539337273283386055832

Offset

1,2

Comments

Column 7 of A220681

Links

R. H. Hardin, Table of n, a(n) for n = 1..107

Example

Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
.00.00.00.00.78.00.00...00.78.00.67.48.68.47...00.00.00.00.68.48.00
.68.48.00.38.27.78.00...38.27.38.00.27.23.78...00.00.68.48.26.24.78
.26.24.00.23.36.24.00...23.00.26.34.00.36.24...00.00.26.24.00.36.24

Crossrefs

Sequence in context: A264262 A232003 A221248 * A189278 A151656 A264088

Adjacent sequences: A220677 A220678 A220679 * A220681 A220682 A220683

Keyword

nonn

Author

R. H. Hardin, Dec 17 2012

Status

approved