PURRS (the Parma University’s Recurrence Relation Solver) is a C++ library for the (possibly approximate) solution of recurrence relations. To be more precise, the PURRS will solve: (a) linear constant coefficient recurrence relations of finite order (when the order is 1, parametric coefficients will be allowed); (b) linear recurrence relations of the first order with variable coefficients; (c) systems of linear recurrence relations with constant coefficients; (d) some non-linear recurrence relations of finite order; (e) some linear recurrence relations of infinite order and other generalized recurrences, like those arising from the complexity analysis of algorithms. (Source: http://freecode.com/)