A220675 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 consecutive collinear links

1, 4, 43, 2024, 468036, 455249977, 2045717834201, 40852471994323068, 3654942390444289784060

Offset

1,2

Comments

Diagonal of A220681

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)
.00.67.47...00.00.00...00.67.48...68.47.00...00.78.78...00.68.48...00.67.48
.38.36.47...00.78.00...38.00.27...23.00.00...38.23.27...68.24.27...36.48.27
.26.34.00...36.24.00...26.34.00...00.00.00...26.34.00...26.34.00...00.23.00

Crossrefs

Sequence in context: A015084 A355081 A176827 * A222979 A284192 A278798

Adjacent sequences: A220672 A220673 A220674 * A220676 A220677 A220678

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved