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A334707
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Number of non-collinear triples in a 5 X n rectangular grid.
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2
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0, 100, 412, 1056, 2148, 3820, 6176, 9352, 13456, 18612, 24940, 32568, 41596, 52164, 64384, 78376, 94256, 112156, 132180, 154464, 179116, 206260, 236016, 268512, 303848, 342164, 383572, 428192, 476140, 527548, 582520, 641192, 703672, 770084, 840548, 915192, 994116
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: 4*x*(25 + 53*x + 83*x^2 + 87*x^3 + 67*x^4 + 35*x^5 + 10*x^6)/((1 - x)^4*(1 + 2*x + 3*x^2 + 3*x^3 + 2*x^4 + x^5)).
a(n) = 2*a(n-1) - a(n-2) + a(n-3) - a(n-4) - a(n-5) + a(n-6) - a(n-7) + 2*a(n-8) - a(n-9) for n > 9. (End)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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