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A073782 a(n) = Sum_{k=0..n} S(k)*S(n-k), convolution of S=A001644 with itself. 1
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
G.f.: (3-2*x-x^2)^2/(1-x-x^2-x^3)^2.
MATHEMATICA
CoefficientList[Series[(3-2x-x^2)^2/(1-x-x^2-x^3)^2, {x, 0, 30}], x]
PROG
(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
CROSSREFS
Cf. A001644.
Sequence in context: A272960 A040074 A088999 * A156033 A196005 A196002
KEYWORD
easy,nonn
AUTHOR
Mario Catalani (mario.catalani(AT)unito.it), Aug 11 2002
STATUS
approved

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)