A220561 Number of ways to reciprocally link elements of an nX7 array either to themselves or to exactly one horizontal or antidiagonal neighbor

21, 1544, 101052, 6743873, 449429440, 29955561052, 1996515036228, 133064181801048, 8868465829053416, 591065515195237024, 39393331961841054032, 2625486595153945514656, 174983417444316851450400

Offset

1,1

Comments

Column 7 of A220562

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 85*a(n-1) -1330*a(n-2) +7350*a(n-3) -15316*a(n-4) +12720*a(n-5) -3168*a(n-6) for n>9

Example

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

Crossrefs

Sequence in context: A035319 A278323 A301432 * A239267 A258305 A081786

Adjacent sequences: A220558 A220559 A220560 * A220562 A220563 A220564

Keyword

nonn

Author

R. H. Hardin Dec 16 2012

Status

approved