A240461 Number of 2 X n 0..3 arrays with no element equal to one plus the sum of elements to its left or three plus the sum of the elements above it or one plus the sum of the elements diagonally to its northwest, modulo 4.

5, 21, 89, 375, 1583, 6685, 28241, 119319, 504151, 2130189, 9000729, 38030999, 160693343, 678981661, 2868918401, 12122113399, 51219871687, 216420616013, 914447487881, 3863838035639, 16325972308111, 68982542575773

Offset: 1

Author

R. H. Hardin, Apr 05 2014

Keywords

• nonn

Examples

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

Links

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

Crossrefs

Row 2 of A240460.

Formula

Empirical: a(n) = 6*a(n-1) - 7*a(n-2) - 4*a(n-3) + 8*a(n-4).

Empirical g.f.: x*(5 - 9*x - 2*x^2 + 8*x^3) / (1 - 6*x + 7*x^2 + 4*x^3 - 8*x^4). - Colin Barker, Oct 29 2018