OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
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 (5,-10,10,-5,1).
FORMULA
From Colin Barker, Apr 20 2012: (Start)
a(n) = (8 - 14*n + 13*n^2 - 4*n^3 + n^4)/4.
G.f.: x*(1 - x + 4*x^2 + 2*x^4)/(1-x)^5. (End)
MATHEMATICA
Table[6Binomial[n, 4]+3Binomial[n, 3]+4Binomial[n, 2]-n+2, {n, 40}] (* or *) LinearRecurrence[{5, -10, 10, -5, 1}, {1, 4, 14, 40, 97}, 40] (* Harvey P. Dale, Feb 05 2017 *)
PROG
(PARI) { for (n=1, 1000, a=6*binomial(n, 4) + 3*binomial(n, 3) + 4*binomial(n, 2) - n + 2; write("b066375.txt", n, " ", a) ) } \\ Harry J. Smith, Feb 11 2010
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jan 04 2002
STATUS
approved