After expanding, the polynomial is in general form. For a polynomial
in general form, I suggest that you use 'coeff' instead of 'ratcoeff' to
find its coefficients. For some cases, coeff will be faster. Consider
(%i1) p : sum(k * x^k,k,1,7000)$
Evaluation took 46.12 seconds (46.12 elapsed)
(%i2) sum(coeff(p,x,k),k,5000,5099)$
Evaluation took 0.87 seconds (0.87 elapsed)
(%i3) sum(ratcoeff(p,x,k),k,5000,5099)$
Evaluation took 27.03 seconds (27.03 elapsed)
Barton