A278189 Number of 2 X n 0..3 arrays with every element plus 1 mod 4 equal to some element at offset (-1,-1) (-1,0) (-1,1) (0,-1) (0,1) or (1,0), with upper left element zero.

0, 3, 19, 136, 935, 6381, 43478, 296105, 2016307, 13729364, 93484479, 636542307, 4334257038, 29512224731, 200950553535, 1368284654492, 9316734157423, 63438214373401, 431954692843542, 2941205998493005, 20026852048660187

Offset: 1

Author

R. H. Hardin, Nov 14 2016

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 2 of A278188.

Formula

Empirical: a(n) = 9*a(n-1) - 16*a(n-2) + 9*a(n-3) - 12*a(n-4) + 5*a(n-5) + 7*a(n-6) - 4*a(n-7).

Empirical g.f.: x^2*(3 - 2*x)*(1 - x + x^2)^2 / (1 - 9*x + 16*x^2 - 9*x^3 + 12*x^4 - 5*x^5 - 7*x^6 + 4*x^7). - Colin Barker, Feb 08 2019