A220628 Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal or antidiagonal neighbors.

1, 1, 3, 37, 1481, 183961, 72097810, 91163971015, 374610359478958, 4999831941923800805, 216409223358914018252290, 30357148112130816204187346595, 13800400036239294148735727438211949

Offset: 1

Author

R. H. Hardin, Dec 17 2012

Keywords

• nonn

Comments

Diagonal of A220632.

Examples

			All solutions for n=3 0=self 3=ne 4=w 6=e 7=sw (reciprocal directions total 10)
.00.67.47...00.00.00...00.00.00
.36.34.00...00.67.47...00.00.00
.00.00.00...36.34.00...00.00.00
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..16