poltschirnhaus() observation

[Igor Schein <igor@txc.com>]

? p=x^5-5*x+12;
? v=vector(16,n,poltschirnhaus(p));
? for(k=1,8,print(v[k]==v[k+8]))
1
1
1
1
1
1
1
1

So the random cycle length in this is 8.  Is it how it's
supposed to be?

Thanks

Igor