>>> r = range(10)
>>> for a in r:
... for b in r:
... for c in r:
... d=a+b;e=b+c;f=d+e
... if len({a,b,c,d,e,f})==6 and a in r and b in r and c in r and d in r and e in r and f in r: # lazy for mathematics
... print(a,b,c,d,e,f)
...
1 2 4 3 6 9
1 3 2 4 5 9
2 1 4 3 5 8
2 1 5 3 6 9
2 3 1 5 4 9
4 1 2 5 3 8
4 2 1 6 3 9
5 1 2 6 3 9