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A206170
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Number of 2 X (n+1) 0..3 arrays with every 2 X 2 subblock in a row having an equal number of equal diagonal or equal antidiagonal elements, adjacent rows differing in this number, and new values 0..3 introduced in row major order.
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2
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15, 85, 641, 5257, 44585, 385465, 3375401, 29817817, 264999305, 2364834745, 21162573161, 189737549977, 1703284356425, 15303437762425, 137574211418921, 1237227532571737, 11129405572871945, 100130796836040505
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OFFSET
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1,1
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COMMENTS
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LINKS
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FORMULA
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Empirical: a(n) = 18*a(n-1) - 101*a(n-2) + 192*a(n-3) - 108*a(n-4).
G.f.: x*(15 - 185*x + 626*x^2 - 576*x^3) / ((1 - x)*(1 - 2*x)*(1 - 6*x)*(1 - 9*x)).
a(n) = (9 + 3*2^n + 2^(1+n)*3^n + 2*9^n) / 3.
(End)
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EXAMPLE
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Some solutions for n=4:
..0..0..1..0..2....0..0..0..0..1....0..0..0..1..2....0..1..2..3..2
..3..2..1..3..3....1..1..1..2..1....0..1..0..0..1....3..1..2..1..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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