A239812 Number of n X 1 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of elements above it, modulo 4.

2, 5, 11, 25, 57, 129, 293, 665, 1509, 3425, 7773, 17641, 40037, 90865, 206221, 468025, 1062197, 2410689, 5471133, 12416905, 28180549, 63956625, 145151533, 329425881, 747642197, 1696797025, 3850933181, 8739811625, 19835272037, 45016761649

Offset

1,1

Comments

Column 1 of A239819.

Links

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

Formula

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

Empirical g.f.: x*(2 + 3*x + 2*x^2) / (1 - x - 2*x^2 - 2*x^3). - Colin Barker, Feb 21 2018

Example

Some solutions for n=5:
..2....2....2....2....3....2....2....3....2....3....2....2....3....3....2....3
..1....1....2....2....1....1....1....3....2....1....1....1....2....3....2....2
..3....2....3....2....2....3....2....2....2....3....2....3....1....1....2....3
..1....1....2....1....1....1....3....3....1....3....1....1....1....3....2....2
..1....2....1....2....1....3....3....3....3....1....1....2....2....1....3....2

Crossrefs

Cf. A239819.

Sequence in context: A356846 A094981 A304969 * A097779 A319768 A366095

Adjacent sequences: A239809 A239810 A239811 * A239813 A239814 A239815

Keyword

nonn

Author

R. H. Hardin, Mar 27 2014

Status

approved