A203373 Number of (n+1) X 4 0..1 arrays with every 2 X 2 subblock having equal diagonal elements or equal antidiagonal elements.

108, 748, 5208, 36300, 253068, 1764360, 12301020, 85762188, 597930552, 4168748268, 29064349260, 202635502632, 1412766774396, 9849754525644, 68672102130648, 478779201937548, 3338029812632076, 23272612897409352

Offset: 1

Author

R. H. Hardin, Dec 31 2011

Keywords

• nonn

Comments

Column 3 of A203378.

Examples

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

Links

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

Crossrefs

Cf. A203378.

Formula

Empirical: a(n) = 9*a(n-1) -15*a(n-2) +6*a(n-3).

Empirical g.f.: 4*x*(27 - 56*x + 24*x^2) / (1 - 9*x + 15*x^2 - 6*x^3). - Colin Barker, Jun 04 2018