A239980 Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or two plus the sum of elements above it or one plus the sum of the elements diagonally to its northwest, modulo 4.

1, 3, 6, 16, 40, 84, 208, 474, 1047, 2530, 5668, 12907, 30446, 68427, 157875, 366480, 830089, 1920870, 4421253, 10083067, 23303103, 53453752, 122448587, 282350403, 647215090, 1486007814, 3420002865, 7842656682, 18022838258, 41428828907

Offset: 1

Author

R. H. Hardin, Mar 30 2014

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Column 2 of A239986.

Formula

Empirical: a(n) = 2*a(n-2) + 10*a(n-3) - a(n-4) - 5*a(n-5) - 15*a(n-6) + a(n-7) + 4*a(n-8) + 2*a(n-9) + 10*a(n-10) + 5*a(n-11) - 6*a(n-13).

Empirical g.f.: x*(1 + 3*x + 4*x^2 - x^4 + 4*x^6 - 4*x^7 - 6*x^8 + 6*x^9 + 6*x^10 - 4*x^12) / (1 - 2*x^2 - 10*x^3 + x^4 + 5*x^5 + 15*x^6 - x^7 - 4*x^8 - 2*x^9 - 10*x^10 - 5*x^11 + 6*x^13). - Colin Barker, Oct 26 2018