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A240193
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Number of 3 X n 0..3 arrays with no element equal to zero plus the sum of elements to its left or one plus the sum of the elements above it or three plus the sum of the elements diagonally to its northwest, modulo 4.
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1
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3, 12, 37, 129, 478, 1908, 7868, 32888, 138292, 583040, 2461028, 10393720, 43907108, 185502448, 783769556, 3311604104, 13992449972, 59122342816, 249810507844, 1055529401752, 4459952527044, 18844744947024, 79625166220340
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OFFSET
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1,1
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LINKS
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FORMULA
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Empirical: a(n) = 9*a(n-1) - 27*a(n-2) + 29*a(n-3) + 6*a(n-4) - 32*a(n-5) + 16*a(n-6) for n>9.
Empirical g.f.: x*(3 - 15*x + 10*x^2 + 33*x^3 - 50*x^4 + 40*x^5 - 25*x^6 - 52*x^7 + 72*x^8) / ((1 - x)*(1 - 2*x)*(1 - 6*x + 7*x^2 + 4*x^3 - 8*x^4)). - Colin Barker, Oct 27 2018
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EXAMPLE
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Some solutions for n=4:
..2..0..0..0....2..0..0..0....2..0..0..0....2..0..0..0....2..0..0..0
..1..3..2..0....2..3..2..0....1..2..0..0....1..2..2..0....1..0..0..2
..1..3..2..3....2..3..2..0....1..2..2..0....1..2..1..3....2..3..0..0
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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