A220646 Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two king-move neighbors, without 3-loops

1, 4, 333, 192413, 1233993907, 85240331175084

Offset

1,2

Comments

Diagonal of A220652

Links

Table of n, a(n) for n=1..6.

Example

Some solutions for n=3 0=self 1=nw 2=n 3=ne 4=w 6=e 7=sw 8=s 9=se (reciprocal directions total 10)
.00.69.47...68.49.00...68.46.48...89.68.48...68.46.48...00.78.00...00.89.00
.89.37.18...26.48.18...26.47.27...29.12.27...29.89.28...38.26.48...68.24.17
.23.16.24...00.26.24...36.34.00...00.13.00...00.12.12...26.46.24...26.34.00

Crossrefs

Sequence in context: A135442 A086895 A293241 * A352657 A173367 A214161

Adjacent sequences: A220643 A220644 A220645 * A220647 A220648 A220649

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved