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A238236
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Expansion of (1-x-x^2)/((x-1)*(x^3+3*x^2+2*x-1)).
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3
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1, 2, 6, 18, 55, 169, 520, 1601, 4930, 15182, 46754, 143983, 443409, 1365520, 4205249, 12950466, 39882198, 122821042, 378239143, 1164823609, 3587185688, 11047081345, 34020543362, 104769516446, 322647744322, 993624581343, 3059961912097, 9423445312544
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OFFSET
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0,2
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COMMENTS
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Row sums of the triangle in A152440.
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LINKS
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FORMULA
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G.f.: (1-x-x^2)/(1-3*x-x^2+2*x^3+x^4).
a(n) = 3*a(n-1) + a(n-2) -2*a(n-3) - a(n-4), a(0) = 1, a(1) = 2, a(2) = 6, a(3) = 18.
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MATHEMATICA
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CoefficientList[Series[(1 - x - x^2)/(1 - 3 x - x^2 + 2 x^3 + x^4), {x, 0, 40}], x ](* Vincenzo Librandi, Feb 22 2014 *)
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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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