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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

G. C. Greubel, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (2,1,0,-3,-2,-1).

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

Adjacent sequences:  A073779 A073780 A073781 * A073783 A073784 A073785

KEYWORD

easy,nonn

AUTHOR

Mario Catalani (mario.catalani(AT)unito.it), Aug 11 2002

STATUS

approved

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Last modified January 16 18:17 EST 2022. Contains 350376 sequences. (Running on oeis4.)