I'm having trouble interpreting the following result of
RSolve to this difference equation:
RSolve[n1 F[n1+1, n2] == (n1+n2) F[n1, n2] + F[n1-1, n2+1] - F[n1, n2+1], F[n1, n2], n1]
The result makes no sense to me, since it is expressed as a sum over
K starting at
K = 0 causing the factorial
(-1 + K)! to diverge.
Is there some special interpretation of this factorial?