A220631 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly two horizontal or antidiagonal neighbors.

1, 32, 564, 10695, 201903, 3817452, 72097810, 1362188752, 25734606523, 486186026515, 9185167500820, 173528846174065, 3278357276282501, 61935676290875214, 1170106754973419295, 22105996097313109325

Offset: 1

Author

R. H. Hardin Dec 17 2012

Keywords

• nonn

Comments

Column 7 of A220632

Examples

			Some solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
.00.00.00.00.00.67.47...00.67.47.67.47.67.47...00.67.46.47.00.67.47
.00.00.00.00.37.36.47...36.34.37.37.36.34.00...36.46.34.00.37.37.00
.00.00.00.36.46.34.00...00.36.34.00.00.00.00...00.00.00.36.34.00.00
		

Links

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

Formula

Empirical: a(n) = 11*a(n-1) +119*a(n-2) +510*a(n-3) +1074*a(n-4) +735*a(n-5) -1120*a(n-6) -2716*a(n-7) +5687*a(n-8) -4250*a(n-9) +1973*a(n-10) -802*a(n-11) +244*a(n-12) -36*a(n-13) -4*a(n-14)