How many types of gametes does an organism heterozygous in four ways form?

16 types of gametes

The diheterozygote gives 4 types of gametes; the triheterozygote gives 8 types of gametes; heterozygous on four grounds – forms 16 types of gametes.
The number of gametes is 2n, where n is not the number of heterozygous gene pairs, but the number of pairs of heterogeneous chromosomes containing heterozygous genes. For example, the triheterozygote AaBbCc will produce 8 types of gametes if the genes are located in different pairs of chromosomes (n = 3) and only 2 types if the genes are in the same pair (n = 1).