A228750 Number of n X 4 binary arrays with top left element equal to 1 and no two ones adjacent horizontally or antidiagonally.

3, 20, 126, 780, 4808, 29608, 182288, 1122240, 6908896, 42533440, 261849728, 1612032128, 9924194048, 61096565760, 376130326016, 2315580595200, 14255467112448, 87761291061248, 540287045521408, 3326182739886080

Offset: 1

Author

R. H. Hardin, Sep 02 2013

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 4 of A228754.

Formula

Empirical: a(n) = 8*a(n-1) - 12*a(n-2) + 4*a(n-3).

Empirical g.f.: x*(3 - 4*x + 2*x^2) / (1 - 8*x + 12*x^2 - 4*x^3). - Colin Barker, Sep 12 2018