A206231 Number of (n+1) X 2 0..3 arrays with every 2 X 3 or 3 X 2 subblock having exactly two equal edges, and new values 0..3 introduced in row major order.

15, 60, 310, 1640, 8910, 51066, 294546, 1710184, 10051522, 59273370, 350336326, 2076929912, 12328636710, 73241168202, 435453806538, 2590088923960, 15409982499130, 91703551575882, 545793722630878, 3248685323916392

Offset: 1

Author

R. H. Hardin, Feb 05 2012

Keywords

• nonn

Comments

Column 1 of A206238.

Examples

			Some solutions for n=4:
..0..1....0..0....0..1....0..0....0..0....0..1....0..1....0..0....0..0....0..0
..0..0....0..1....0..0....0..1....1..0....2..1....2..0....1..1....0..1....0..1
..0..1....1..2....0..1....1..0....0..1....3..1....0..0....2..1....1..2....1..2
..1..2....1..1....1..0....0..0....0..0....0..1....3..0....1..0....2..2....1..1
..1..1....0..1....0..0....2..2....0..2....3..3....2..1....0..0....1..1....0..0
		

Links

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

Crossrefs

Cf. A206238.

Formula

Empirical: a(n) = 8*a(n-1) -11*a(n-2) +36*a(n-3) -303*a(n-4) +232*a(n-5) +147*a(n-6) +756*a(n-7) for n>8.

Empirical g.f.: x*(15 - 60*x - 5*x^2 - 720*x^3 + 1585*x^4 + 1366*x^5 + 2793*x^6 - 378*x^7) / ((1 - 4*x)*(1 - x - x^2 - 3*x^3)*(1 - 3*x - 7*x^2 - 63*x^3)). - Colin Barker, Jun 14 2018