polroots: impossible inverse

[Gordon Royle <gordon.royle@uwa.edu.au>]

I have just compiled Pari/GP for Mac OS X (10.7) from source.

When I try

p = 0+(0*x^0)+(0*x^1)+(11*x^2)+(-25*x^3)+(20*x^4)+(-7*x^5)+(1*x^6);
polrootsâ

I get

? polroots(p)
  ***   at top-level: polroots(p)
  ***                 ^-----------
  *** polroots: impossible inverse modulo: Mod(4, 27457).
  ***   Break loop: type 'break' to go back to GP


Why is this?


Professor Gordon Royle
School of Mathematics and Statistics
University of Western Australia
Gordon.Royle@uwa.edu.au