Say you want to consider all four bases (i.e. 2,3,5,7), the number of factors are 3*2*4*1=24
Say you to consider a particular 3-member combination of these four, the number of factors will be 3*2*4+2*4*1+3*4*1+3*2*1=50
Say you want to consider a particular 2-member combination of these four...