|
|
A026032
|
|
a(n) = C(3n,n) - C(3n,n-4).
|
|
0
|
|
|
1, 3, 15, 84, 494, 2988, 18411, 114950, 724845, 4606095, 29451240, 189264672, 1221417360, 7910510312, 51388786107, 334716829674, 2185180379179, 14294808917025, 93680975707935, 614925987859260, 4042236129950970
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,2
|
|
LINKS
|
|
|
FORMULA
|
G.f.: (2*g-1)*(2*g^2-2*g+1)/((3*g-1)*(g-1)^4) where g*(1-g)^2 = x. - Mark van Hoeij, Nov 09 2011
|
|
MATHEMATICA
|
Table[Binomial[3n, n]-Binomial[3n, n-4], {n, 0, 20}] (* Harvey P. Dale, Dec 14 2012 *)
|
|
PROG
|
(PARI) a(n) = binomial(3*n, n) - binomial(3*n, n-4); \\ Michel Marcus, May 10 2020
|
|
CROSSREFS
|
a(n) = T(3n, n), where T is defined in A026022.
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|