A063823 Expansion of g.f. (1 - 2*x^2 - 3*x^3)/((1 - x^3)*(1 - 2*x)).

1, 2, 2, 2, 4, 6, 10, 20, 38, 74, 148, 294, 586, 1172, 2342, 4682, 9364, 18726, 37450, 74900, 149798, 299594, 599188, 1198374, 2396746, 4793492, 9586982, 19173962, 38347924, 76695846, 153391690, 306783380, 613566758, 1227133514, 2454267028, 4908534054, 9817068106

Offset

0,2

References

P. de la Harpe, Topics in Geometric Group Theory, Univ. Chicago Press, 2000, p. 259.

Links

Table of n, a(n) for n=0..36.

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

Formula

E.g.f.: exp(-x/2)*(exp(3*x/2)*(28 + 3*exp(x)) - 10*cos(sqrt(3)*x/2) + 2*sqrt(3)*sin(sqrt(3)*x/2))/21. - Stefano Spezia, May 30 2023

Mathematica

LinearRecurrence[{2, 0, 1, -2}, {1, 2, 2, 2}, 37] (* Stefano Spezia, May 30 2023 *)

Crossrefs

Sequence in context: A064355 A000799 A185030 * A182027 A005865 A176051

Adjacent sequences: A063820 A063821 A063822 * A063824 A063825 A063826

Keyword

nonn,easy

Author

N. J. A. Sloane, Aug 21 2001

Extensions

a(34)-a(36) from Stefano Spezia, May 30 2023

Status

approved