Possible=()
Impossible=()
#Deeeeeelete - Indivisible=()

for n in range(1,100):
    for c in range(0,10):
        for b in range(0,10):
            for a in range(0,10):
                if (6*a)+(9*b)+(20*c)==n:
                    Possible +=(n,)
                    break
            if n in Possible:
                break
        if n in Possible:
            break
    #Put counter conditional here, and then your else clause after it
    if n in possible:
        #Counter stuff
    else:
        #What do you think?

#These are unnecessary now
for m in Impossible:
    if m not in Possible:
        Indivisible +=(m,)

print Possible
print Impossible
#No need for this variable - Indivisible[-1]