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A251367
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Number of (n+1) X (2+1) 0..2 arrays with every 2 X 2 subblock summing to 1, 2, 3, 4, 5, 6, or 7.
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1
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695, 17969, 464393, 12002283, 310199103, 8017100977, 207202101873, 5355141623323, 138403720518311, 3577046360518609, 92448820142650873, 2389341228591410219, 61752562096926105327, 1595995950642355498897
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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) = 24*a(n-1) + 49*a(n-2) - 34*a(n-3).
Empirical formula verified: see link.
G.f.: (695*x+1289*x^2-918*x^3)/(1-24*x-49*x^2+34*x^3). (End)
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EXAMPLE
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Some solutions for n=2:
2 1 1 2 0 2 0 2 1 2 2 2 0 0 2 0 0 2 0 0 2
0 0 0 1 0 0 1 0 1 0 1 1 1 1 2 1 2 1 1 1 1
1 2 2 2 0 1 1 2 1 2 0 2 0 0 1 1 0 1 0 1 0
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MAPLE
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f:= gfun:-rectoproc({a(n) = 24*a(n-1) +49*a(n-2) -34*a(n-3), a(1)=695, a(2)=17969, a(3)=464393}, a(n), remember):
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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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