fix issue #8323

	harmonic(n).evalf() and catalan(n).evalf()
```python
n = self.args[0]
if n.is_number:
    # m = 1 (if not given) else args[1]
    if len(args) == 1 or self.args[1].is_number:
        return self.rewrite(polygamma).evalf(n=prec)
```