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A011926
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a(n) = floor(n*(n-1)*(n-2)*(n-3)/16).
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0
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0, 0, 0, 0, 1, 7, 22, 52, 105, 189, 315, 495, 742, 1072, 1501, 2047, 2730, 3570, 4590, 5814, 7267, 8977, 10972, 13282, 15939, 18975, 22425, 26325, 30712, 35626, 41107, 47197, 53940, 61380, 69564, 78540
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OFFSET
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0,6
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LINKS
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FORMULA
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G.f.: x^4*(x^4+1+2*x-3*x^2+2*x^3) / ((1-x)^5*(x^4+1) ).
a(n) = +5*a(n-1) -10*a(n-2) +10*a(n-3) -6*a(n-4) +6*a(n-5) -10*a(n-6) +10*a(n-7) -5*a(n-8) +a(n-9). (End)
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PROG
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(Magma) [Floor(n*(n-1)*(n-2)*(n-3)/16) : n in [0..100]]; // Wesley Ivan Hurt, Apr 20 2021
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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