To see Melody's answer
Note that......when n = 1
(x^2 + 1/x)^(3*1) = (x^2 + 1/x)^3 will have the term C(3,2)(x^2)^1 * (1/x)^2 = 3x^2(1/x^2)
Constant term = 3
When n = 2.....
(x^2 + 1/x)^(3*2) = (x^2 + 1/x)^6 will have the term C(6, 4)(x^2)^2 * (1/x)^4 = 15 (x^4)(1/x^4)
Constant term = 15
When n = 3....
(x^2 + 1/x)(3 * 3) will have the term C(9, 6) (x^2)^3 *(1/x)^6 = 84 (x^6)(1/x^6)
Constant term = 84
So.....it appears the the pattern for the constant term will be
C(3n, 2n) * (x^2)^n * (1/x)^(2n) where n is a positive integer