A238768 Number of n X 1 0..3 arrays with no element equal to the sum modulo 4 of elements to its left or elements above it.

3, 6, 14, 32, 72, 164, 372, 844, 1916, 4348, 9868, 22396, 50828, 115356, 261804, 594172, 1348492, 3060444, 6945772, 15763644, 35776076, 81194908, 184274348, 418216316, 949154828, 2154136156, 4888878444, 11095460412, 25181489612

Offset

1,1

Comments

Column 1 of A238775.

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*(3 + 3*x + 2*x^2) / (1 - x - 2*x^2 - 2*x^3). - Colin Barker, Feb 24 2018

Example

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

Crossrefs

Cf. A238775.

Sequence in context: A209357 A090165 A129954 * A272362 A182905 A330053

Adjacent sequences: A238765 A238766 A238767 * A238769 A238770 A238771

Keyword

nonn

Author

R. H. Hardin, Mar 05 2014

Status

approved