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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.
1
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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 04 2014
STATUS
approved