The pFqToStandardFunctions(f, k=m..n) command computes a closed form of the definite sum of f over the specified range of k by first converting the specified sum into hypergeometric functions. If possible, the output is then converted to standard functions.

Petkovsek, M.; Wilf, H.; and Zeilberger, D. A=B, Ch. 3. Wellesley, Massachusetts: A K Peters, Ltd., 1996.

Prudnikov, A. P.; Brychkov, Yu.; and Marichev, O. Integrals and Series. Gordon and Breach Science Publishers, 1990. Vol. 3: More Special Functions.

Roach, K. "Hypergeometric Function Representations." Proceedings ISSAC 1996, pp. 301-308. New York: ACM Press, 1996.