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A221859
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Expansion of (1-3*x+x^2)*(1-2*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).
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1
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1, 4, 15, 56, 209, 779, 2898, 10760, 39882, 147612, 545721, 2015721, 7440251, 27448008, 101217076, 373128151, 1375167467, 5067236766, 18669118971, 68774597447, 253334948791, 933111590565, 3436767111783, 12657552835178, 46616152422035, 171677402416052
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OFFSET
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0,2
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COMMENTS
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A diagonal of the square array A223968.
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LINKS
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FORMULA
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G.f.: (1-3*x+x^2)*(1-2*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).
a(n) = 9*a(n-1) - 28*a(n-2) + 35*a(n-3) - 15*a(n-4) + a(n-5) with a(0) = 1, a(1) = 4, a(2) = 15, a(3) = 56, a(4) = 209.
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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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