# RationalFunctionSum R¶

sum(f(n), n = a..b) returns f(a) + f(a+1) + ... f(b).
sum(a(n), n) returns A which is the indefinite sum of a with respect to upward difference on n, i.e. A(n+1) - A(n) = a(n).
sum(f(n), n = a..b) returns f(a) + f(a+1) + ... f(b).
sum(a(n), n) returns A which is the indefinite sum of a with respect to upward difference on n, i.e. A(n+1) - A(n) = a(n).