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A232951
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Number of n X 4 0..3 arrays with no element x(i,j) adjacent to value 3-x(i,j) horizontally, diagonally or antidiagonally, and top left element zero.
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1
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27, 771, 22971, 685251, 20442651, 609853251, 18193384251, 542752261251, 16191600916251, 483034266181251, 14410069980856251, 429886928094781251, 12824557492939156251, 382587290147700781251, 11413495916966327656251
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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) = 31*a(n-1) - 35*a(n-2) + 5*a(n-3).
G.f.: 3*x*(9 - 22*x + 5*x^2) / ((1 - x)*(1 - 30*x + 5*x^2)).
a(n) = (55 + (15-2*sqrt(55))^n*(55+sqrt(55)) - (-55+sqrt(55))*(15+2*sqrt(55))^n)/55.
(End)
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EXAMPLE
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Some solutions for n=3:
..0..0..0..1....0..2..3..1....0..2..3..2....0..0..1..1....0..2..2..2
..0..0..0..2....0..1..0..2....0..2..3..2....2..0..1..3....3..2..2..2
..0..0..0..1....0..2..3..2....0..2..3..1....1..3..2..0....0..2..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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