A220601 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without 3-loops.

1, 305, 190425, 60138423, 16505365334, 4807269151250, 1417058414112748, 415538772723268712, 121740835171119793585, 35681922955520577801844, 10458840906159008629586152, 3065510523366853897987776536

Offset: 1

Author

R. H. Hardin Dec 16 2012

Keywords

• nonn

Comments

Column 7 of A220602

Examples

			Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
.00.00.00.00.00.00.78...00.67.48.68.48.00.78...00.78.00.00.67.46.48
.00.00.00.68.46.34.28...36.48.27.28.26.34.27...38.28.00.38.78.78.28
.00.00.00.26.46.46.24...00.23.00.26.46.34.00...26.24.00.23.23.26.24
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..116