Consider
from sage.calculus.calculus import symbolic_sum
n = var('n')
print 1/(1 + symbolic_sum(factorial(n) * x^n, n, 1, oo))
Answer of Sage 7.4:
1/(x*hypergeometric((1, 2), (), x) + 1)
Answer of Sage 8.0:
ValueError: Computation failed since Maxima requested
additional constraints; ....
