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A238991
Number of n X 2 0..3 arrays with no element equal to two plus the sum of elements to its left or two plus the sum of the sum of elements above it, modulo 4.
1
7, 41, 203, 955, 4393, 20015, 90841, 411621, 1863915, 8437893, 38193735, 172873711, 782450381, 3541446587, 16028869589, 72547812889, 328356354383, 1486162751697, 6726470705667, 30444448197731, 137793568150513, 623662712572871
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) + a(n-2) - 48*a(n-3) + 49*a(n-4) + 70*a(n-5) - 77*a(n-6) - 68*a(n-7) + 52*a(n-8) + 16*a(n-9).
Empirical g.f.: x*(7 - x - 50*x^2 + 32*x^3 + 85*x^4 - 53*x^5 - 80*x^6 + 52*x^7 + 16*x^8) / ((1 - x)*(1 - 2*x)*(1 - 3*x - 12*x^2 + 18*x^3 + 29*x^4 - 19*x^5 - 38*x^6 - 8*x^7)). - Colin Barker, Oct 24 2018
EXAMPLE
Some solutions for n=5:
..0..3....0..1....3..0....3..0....0..3....0..1....3..0....0..3....0..1....3..0
..3..2....3..0....0..0....3..0....3..3....0..0....0..0....0..3....0..0....0..3
..3..0....3..0....0..0....3..3....0..1....0..1....0..3....1..2....3..0....3..0
..1..2....1..0....0..0....1..2....3..2....0..1....3..3....1..1....3..0....1..0
..3..0....3..0....0..1....1..0....3..2....1..0....3..3....1..1....1..1....0..3
CROSSREFS
Column 2 of A238997.
Sequence in context: A237854 A219862 A366996 * A084779 A266887 A237664
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 08 2014
STATUS
approved