var('x,y,z')
g(x,y,z)=x^20+y^20+z^20
q(a,b,c)=0
for n in range(8):
    f(x,y)=g(x,y,0)
    p(a,b)=0
    for m in range(11):
        p(a,b)=p(a,b)+f(a,0)*b^m
        f(x,y)=expand((f(x,y)-f(x+y,0))/x/y)
    q(a,b,c)=q(a,b,c)+p(a,b)*c^n
    g(x,y,z)=expand((g(x,y,z)-p(x+y+z,x*y+x*z+y*z))/x/y/z) 
print (expand(q(x+y+z,x*y+x*z+y*z,x*y*z)))