[pstricks] [OT] A macro for typesetting nPr (permutations)?

[Hubert Lam]

Does anyone know of a macro in (AMS)LaTeX that has the symbol for nPr?

I understand that \binom{n}{r} and its variants, but there seems to be 
nothing for nPr.

The manual (and perhaps clumsy) way I've been using is

$^n P_r$

Many thanks,

Hubert