A220687 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors.

1, 1081, 362057, 128995678, 42362190063, 14108684022136, 4701615485821782, 1566852499542855296, 522108399243273023731, 173978947909208417520148, 57974051497341052095013087, 19318375776055542860988503113

Offset: 1

Author

R. H. Hardin Dec 17 2012

Keywords

• nonn

Comments

Column 7 of A220688

Examples

			Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
.00.00.67.46.46.47.00...00.00.00.00.68.48.00...00.00.68.48.68.46.48
.00.36.46.47.37.67.47...00.67.48.00.27.26.47...00.78.28.28.26.47.28
.00.00.36.34.36.34.00...36.46.24.36.46.34.00...36.24.26.24.36.46.24
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..114