A207402 Number of n X 7 0..1 arrays avoiding 0 0 1 and 0 1 1 horizontally and 0 0 1 and 1 1 0 vertically.

20, 400, 2340, 8910, 26676, 68060, 154580, 321110, 621300, 1134296, 1972900, 3293310, 5306580, 8291940, 12612116, 18730790, 27232340, 38844000, 54460580, 75171886, 102292980, 137397420, 182353620, 239364470, 311010356, 400295720

Offset: 1

Author

R. H. Hardin, Feb 17 2012

Keywords

• nonn

Comments

Column 7 of A207403.

Examples

			Some solutions for n=4:
..0..0..0..0..0..0..0....0..1..0..1..0..0..0....1..1..1..1..1..1..1
..1..1..1..0..0..0..0....0..1..0..1..0..0..0....0..1..0..1..0..0..0
..0..0..0..0..0..0..0....0..1..0..1..0..0..0....1..1..1..1..1..1..1
..1..0..0..0..0..0..0....0..1..0..1..0..0..0....0..1..0..1..0..0..0
		

Links

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

Crossrefs

Cf. A207403.

Formula

Empirical: a(n) = (1/36)*n^7 + (4/9)*n^6 + (53/18)*n^5 + (91/9)*n^4 + (589/36)*n^3 + (31/9)*n^2 - (58/3)*n + 6.

Conjectures from Colin Barker, Jun 22 2018: (Start)

G.f.: 2*x*(10 + 120*x - 150*x^2 + 135*x^3 - 42*x^4 - 14*x^5 + 14*x^6 - 3*x^7) / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>8.

(End)