A205312 Number of (n+1) X 3 0..1 arrays with every 2 X 2 subblock having the same number of equal edges, and new values 0..1 introduced in row major order.

20, 84, 376, 1708, 7784, 35500, 161928, 738636, 3369320, 15369324, 70107976, 319801228, 1458790184, 6654348460, 30354161928, 138462112716, 631602239720, 2881086973164, 13142230386376, 59948977985548, 273460429154984

Offset: 1

Author

R. H. Hardin, Jan 25 2012

Keywords

• nonn

Comments

Column 2 of A205318.

Examples

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

Links

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

Crossrefs

Cf. A205318.

Formula

Empirical: a(n) = 6*a(n-1) -7*a(n-2) +2*a(n-3).

Empirical g.f.: 4*x*(5 - 9*x + 3*x^2) / ((1 - x)*(1 - 5*x + 2*x^2)). - Colin Barker, Jun 11 2018