Fractional BPS multitrace fields of N=4 SYM4 from AdS/CFT

We prove inductively that every k-trace operator of SO(6)R irrep with Young tableau partition {r1,r2,r3}, constructed out of k chiral primaries in the twenty-dimensional SO(6)R irrep, leads to a quasi primary field with protected conformal dimension. Our argument is based on perturbative evaluations of certain four-point functions up to order 1/N2.