Software for recurrence relations

Question

What software do you use and would recommend for solving recurrence relations?

For example mathematica has RSolve:

$ a(n+1)-2 a(n) = 1$ for $a(n)$:

RSolve[a[n + 1] - 2 a[n] == 1, a[n], n]
-> a(n) = c 2^(n-1)+2^n-1

Are there any good (preferably open) alternatives?

Answer 1

WolframAlpha does an okay job.