no of terms in (1+x+x^3)^10. ??

inside terms are 1,x,x^3
that means we have total of 3 terms
and outside we are having 10th power
so total number of terms we will get are = { [ 10 + ( 3 - 1 ) ] ! } / [ ( 10 ! ) ( ( 3 - 1) ! ) ) ]
= 66
so total number of terms were 66