Ways to sum 7 integers to get 21

import math
k=0
i = 1
numbers = 7
S = 21
t = S- numbers
R = math.floor(math.log(S))

for a in range(1,t):
    for b in range(a,t-a):
        for c in range(b,t-a-b):
            for d in range(c,t-a-b-c):
                for e in range(d,t-a-b-c-d):
                    for f in range(e,t-a-b-c-d-e):
                        g = S-a-b-c-d-e-f
                        if g>f:
                            s = a+b+c+d+e+f+g
                            i = i + 1
                            print(repr(a).rjust(R),' +',repr(b).rjust(R),
                              ' +',repr(c).rjust(R),' +',repr(d).rjust(R),
                              ' +',repr(e).rjust(R),' +',repr(f).rjust(R),
                              ' +',repr(g).rjust(R),' = ',repr(s).rjust(1))
print(i)