Let P be a polynomial with integer coefficients such that P(0)=0 and
gcd(P(0),P(1),P(2),…)=1.
We need to show that there are infinitely many n such that
gcd(P(n)−P(0),P(n+1)−P(1),P(n+2)−P(2),…)=n.
Consider the polynomial P(x)=xkQ(x), where Q(0)=0. We claim that if n=pk for any prime p not dividing kQ(1)+Q′(1), then n will satisfy the conditions of the problem.
It is clear that pk∣P(pk+i)−P(i) for all i, hence pk∣gcd(P(pk+i)−P(0),P(pk+1)−P(1),P(pk+2)−P(2),…). We now claim that pk+1∤P(pk+1)−P(1). Let Q(x)=∑i=0mcixi, then
P(pk+1)−P(1)=(pk+1)kQ(pk+1)−Q(1)=(i=0∑k(ik)(pk)i)Q(pk+1)−Q(1)≡(kpk+1)Q(pk+1)−Q(1)=kpkQ(pk+1)+(Q(pk+1)−Q(1))=kpkQ(pk+1)+i=0∑mci((pk+1)i−1i)=kpkQ(pk+1)+i=0∑mci(−1+j=0∑i(ji)(pk)j)≡kpkQ(pk+1)+i=0∑micipk=pk(kQ(pk+1)+Q′(1))(modpk+1).
Thus,
pkP(pk+1)−P(1)=kQ(pk+1)+Q′(1)≡kQ(1)+Q′(1)≡0(modp),
so pk fully divides gcd(P(pk+i)−P(0),P(pk+1)−P(1),P(pk+2)−P(2),…).
To show that no other prime q=p divides each of P(pk)−P(0),P(pk+1)−P(1),P(pk+2)−P(2),…, suppose for contradiction that q∣P(pk+i)−P(i) for all positive integers i. Observing that q∣P(q+i)−P(i), we find that P(i+apk+bq)≡P(i)(modq) for all integers a and b. Since gcd(pk,q)=1, we can choose a and b such that apk+bq=1, yielding q∣P(i+1)−P(i) for all i. But q∣P(0)=0, so q∣P(i) for all nonnegative i, which contradicts the hypothesis.
Therefore, there are infinitely many n such that
gcd(P(n)−P(0),P(n+1)−P(1),P(n+2)−P(2),…)=n.
The answer is: \boxed{\text{infinitely many } n}.