sympy/sympy — pull request #1842 by skirpichev (2013-02-26 15:11:42+00:00)
Title: rsolve: use limit() to substitute initial values of n in the generic solution of the recurrence equation

Using just subs() rsolve sometimes is not able to find solution with specified initial conditions.

An example in master:
```
In [1]: f = (-16*n**2 + 32*n - 12)*y(n - 1) + (4*n**2 - 12*n + 9)*y(n)

In [2]: rsolve(f, y(n), {y(1): binomial(2*n + 1, 3)})
Out[2]: 0

In [3]: g=rsolve(f, y(n))

In [4]: g.subs(n,1)
Out[4]: ∞⋅C₀
In [5]: g
Out[5]:
-n n - 1
2 ⋅8 ⋅C₀⋅(n - 1/2)!
────────────────────────
(n - 3/2)!
In [6]: g.limit(n,1)
Out[6]:
C₀
──
4
```