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A073782
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a(n) = Sum_{k=0..n} S(k)*S(n-k), convolution of S=A001644 with itself.
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1
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9, 6, 19, 48, 89, 190, 391, 784, 1577, 3142, 6219, 12256, 24041, 46974, 91471, 177568, 343753, 663814, 1278979, 2459152, 4719417, 9041470, 17294039, 33030320, 62999145, 120006214, 228327099, 433939904, 823854793, 1562602238
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OFFSET
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0,1
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LINKS
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FORMULA
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G.f.: (3-2*x-x^2)^2/(1-x-x^2-x^3)^2.
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MATHEMATICA
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CoefficientList[Series[(3-2x-x^2)^2/(1-x-x^2-x^3)^2, {x, 0, 30}], x]
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PROG
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(PARI) my(x='x+O('x^30)); Vec((3-2*x-x^2)^2/(1-x-x^2-x^3)^2) \\ G. C. Greubel, Apr 12 2019
(Magma) R<x>:=PowerSeriesRing(Integers(), 30); Coefficients(R!( (3-2*x-x^2)^2/(1-x-x^2-x^3)^2 )); // G. C. Greubel, Apr 12 2019
(Sage) ((3-2*x-x^2)^2/(1-x-x^2-x^3)^2).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, Apr 12 2019
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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Mario Catalani (mario.catalani(AT)unito.it), Aug 11 2002
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STATUS
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approved
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