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

Author

R. H. Hardin Dec 16 2012

Keywords

• nonn

Comments

Column 7 of A220562

Examples

			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
		

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