A240428 Number of n X 2 0..3 arrays with no element equal to zero plus the sum of elements to its left or zero plus the sum of elements above it or two plus the sum of the elements diagonally to its northwest, modulo 4.

2, 6, 24, 58, 236, 566, 2322, 5578, 22912, 55054, 226148, 543394, 2232094, 5363294, 22030696, 52935498, 217442092, 522471270, 2146144946, 5156771098, 21182367216, 50897130430, 209069141604, 502352700210, 2063504305918, 4958201635918

Offset

1,1

Links

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

Formula

Empirical: a(n) = 12*a(n-2) - 24*a(n-4) + 31*a(n-6) - 16*a(n-8).

Empirical g.f.: 2*x*(1 - x)*(1 + 4*x + 4*x^2 - 3*x^3 - 5*x^4 + 2*x^5 + 4*x^6) / (1 - 12*x^2 + 24*x^4 - 31*x^6 + 16*x^8). - Colin Barker, Oct 27 2018

Example

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

Crossrefs

Column 2 of A240433.

Sequence in context: A175624 A289161 A118038 * A276838 A364424 A022917

Adjacent sequences: A240425 A240426 A240427 * A240429 A240430 A240431

Keyword

nonn

Author

R. H. Hardin, Apr 04 2014

Status

approved