A220687 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly two horizontal, vertical or antidiagonal neighbors

1, 1081, 362057, 128995678, 42362190063, 14108684022136, 4701615485821782, 1566852499542855296, 522108399243273023731, 173978947909208417520148, 57974051497341052095013087, 19318375776055542860988503113

Offset

1,2

Comments

Column 7 of A220688

Links

R. H. Hardin, Table of n, a(n) for n = 1..114

Example

Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)
.00.00.67.46.46.47.00...00.00.00.00.68.48.00...00.00.68.48.68.46.48
.00.36.46.47.37.67.47...00.67.48.00.27.26.47...00.78.28.28.26.47.28
.00.00.36.34.36.34.00...36.46.24.36.46.34.00...36.24.26.24.36.46.24

Crossrefs

Sequence in context: A251199 A220334 A221295 * A188240 A165809 A332069

Adjacent sequences: A220684 A220685 A220686 * A220688 A220689 A220690

Keyword

nonn

Author

R. H. Hardin Dec 17 2012

Status

approved