A220630 Number of ways to reciprocally link elements of an nX6 array either to themselves or to exactly two horizontal or antidiagonal neighbors.

1, 16, 158, 1665, 17527, 183961, 1932695, 20301254, 213251377, 2240062837, 23530357757, 247170637157, 2596361852466, 27273040848960, 286485012144200, 3009333012881404, 31611026051882958, 332052638832405598

Offset: 1

Author

R. H. Hardin Dec 17 2012

Keywords

• nonn

Comments

Column 6 of A220632

Examples

			Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
.00.67.46.46.46.47...00.00.67.46.46.47...00.00.00.00.67.47...00.00.67.47.00.00
.36.46.47.00.37.00...00.36.46.47.37.00...00.00.00.36.34.00...00.37.37.67.46.47
.00.36.46.34.00.00...00.00.36.34.00.00...00.00.00.00.00.00...36.34.36.46.34.00
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 7*a(n-1) +31*a(n-2) +57*a(n-3) +43*a(n-4) -3*a(n-5) -36*a(n-6) +19*a(n-7) -6*a(n-8) +a(n-9)