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

1,2

Comments

Column 7 of A220632

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)

Example

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

Crossrefs

Sequence in context: A178372 A082557 A022660 * A304308 A316207 A305774

Adjacent sequences: A220628 A220629 A220630 * A220632 A220633 A220634

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved