BUG: special: pbvv_seq is broken. #17681
Description
The function scipy.special.pbvv_seq fails to run:
In [1]: import scipy
In [2]: scipy.__version__
Out[2]: '1.11.0.dev0+1208.2af3085'
In [3]: from scipy.special import pbvv_seq
In [4]: pbvv_seq(3, 1.5)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
Cell In [4], line 1
----> 1 pbvv_seq(3, 1.5)
File ~/repos/git/forks/scipy/build-install/lib/python3.10/site-packages/scipy/special/_basic.py:2235, in pbvv_seq(v, x)
2233 n1 = n
2234 v1 = n1 + v0
-> 2235 dv, dp, pdf, pdd = _specfun.pbvv(v1, x)
2236 return dv[:n1+1], dp[:n1+1]
AttributeError: module 'scipy.special._specfun' has no attribute 'pbvv'
This function has no tests, otherwise we would have caught this issue a long time ago. I don't know how long it has been broken. If it has never worked, we could consider simply deleting it. Edit: pbvv_seq was discussed in #4957, so apparently it was working back in 2015.