sympy/sympy — pull request #2342 by skirpichev (2013-07-31 21:31:06+00:00)
Title: Fix for issue 3891

Pow._eval_nseries: do expand_mul for output if b0!=0. Now:
```
In [1]: x,a,b = symbols('x,a,b')

In [2]: (sqrt(a+b*x+x**2)).series(x,0,3)
Out[2]:
⎛ 2 ⎞
b⋅x 2 ⎜ 1 b ⎟ ___ ⎛ 3⎞
─────── + x ⋅⎜─────── - ──────⎟ + ╲╱ a + O⎝x ⎠
___ ⎜ ___ 3/2⎟
2⋅╲╱ a ⎝2⋅╲╱ a 8⋅a ⎠

```