From: Diplotyper: diplotype-based association analysis
Input
H = {A, B, C, D}, HS = {{A}, {B}, {C}, {D}}, repeat frequency = 0
Output
HS = {{A}, {B}, {C}, {D}, {A, B}, {A, C}, {A, D}, {B, C}, {B, D}, {C, D}, {A, B, C}, {A, B, D}, {A, C, D}, {B, C, D}, {A, B, C, D}}