A220596 Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without 3-loops

1, 2, 65, 9047, 7558495, 41011388731, 1417058414112748, 305516864725171735943, 412489181606705015322075070

Offset

1,2

Comments

Diagonal of A220602

Links

Table of n, a(n) for n=1..9.

Example

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...00.78.78...68.46.47...68.46.48...00.67.48...00.78.00...00.67.47
.00.67.47...38.23.28...28.36.47...28.68.24...38.67.24...38.28.00...38.37.00
.36.34.00...26.46.24...26.34.00...26.24.00...23.00.00...26.24.00...23.00.00

Crossrefs

Sequence in context: A185029 A228081 A214366 * A326253 A003821 A055765

Adjacent sequences: A220593 A220594 A220595 * A220597 A220598 A220599

Keyword

nonn

Author

R. H. Hardin Dec 16 2012

Status

approved