A073782 a(n) = Sum_{k=0..n} S(k)*S(n-k), convolution of S=A001644 with itself.

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

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