OFFSET
0,2
FORMULA
G.f.: (1-2*g)*(g^2-g+1)/((3*g-1)*(g-1)^3) where g*(1-g)^2 = x. - Mark van Hoeij, Nov 09 2011
Conjecture: -2*(2*n+3)*(13*n-9)*(n+1)*a(n) +(499*n^3-7*n^2-120*n-54)*a(n-1) -3*(3*n-5)*(37*n-24)*(3*n-4)*a(n-2)=0. - R. J. Mathar, Jun 20 2013
MATHEMATICA
Table[Binomial[3n, n]-Binomial[3n, n-3], {n, 0, 20}] (* Harvey P. Dale, Jun 04 2016 *)
PROG
(PARI) a(n) = binomial(3*n, n) - binomial(3*n, n-3); \\ Michel Marcus, May 10 2020
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 17 2005
STATUS
approved