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A228213
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Number of second differences of arrays of length n + 2 of numbers in 0..3.
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2
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13, 103, 625, 3151, 14053, 58975, 242461, 989527, 4017157, 16245775, 65514541, 263652487, 1059392917, 4251920575, 17050729021, 68332056247, 273715645477, 1096024843375, 4387586157901, 17560804984807, 70274600998837
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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) = 7*a(n-1) - 12*a(n-2) = A005061(n+2) for n>7.
G.f.: x*(13 + 12*x + 60*x^2 + 12*x^3 - 504*x^4 - 1584*x^5 - 1728*x^6) / ((1 - 3*x)*(1 - 4*x)).
a(n) = 4^(2+n) - 3^(2+n) for n>5.
(End)
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EXAMPLE
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Some solutions for n=4:
..5....0...-5....3....4....1....3...-3...-6....2....2....1...-5....1....0....2
.-4....2....2...-3...-5....1....1....3....3...-1....3....1....3....4....3....1
..2....0...-1....5....5...-3...-5....1....1....4...-5....1....0...-6...-3...-1
..3...-2....2...-6...-2....0....3...-5....1...-5....4...-1...-3....6....3....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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