A066368 a(n) = (n+2)*2^(n-1) - 2*n.

1, 1, 4, 14, 40, 102, 244, 562, 1264, 2798, 6124, 13290, 28648, 61414, 131044, 278498, 589792, 1245150, 2621404, 5504986, 11534296, 24117206, 50331604, 104857554, 218103760, 452984782, 939524044, 1946157002, 4026531784, 8321499078, 17179869124, 35433480130, 73014443968

Offset: 0

Author

N. J. A. Sloane, Jan 04 2002

Keywords

• nonn
• easy

Links

• Harry J. Smith, Table of n, a(n) for n = 0..200
• M. Azaola and F. Santos, The number of triangulations of the cyclic polytope C(n,n-4), Discrete Comput. Geom., 27 (2002), 29-48.
• Index entries for linear recurrences with constant coefficients, signature (6,-13,12,-4).

Programs

Mathematica

Table[(n+2)2^(n-1)-2n,{n,0,30}] (* Harvey P. Dale, Apr 18 2019 *)

PARI

a(n) = { (n + 2)*2^(n - 1) - 2*n } \\ Harry J. Smith, Feb 11 2010

Formula

G.f.: (1-5*x+11*x^2-9*x^3)/((1-x)^2*(1-2*x)^2). - Colin Barker, Apr 19 2012