l=[1,2,3,4]
n=2**len(l)
ssa=[] #sub sequenc earray
print(ssa)
for i in range(1,n):
    ssa=[]
    pos=0 #index of list
    while i!=0:
        if i&1==1:
            ssa.append(l[pos])
            pos=pos+1
            i=i>>1 
        else:
            i=i>>1
            pos=pos+1
    print(ssa)