Function: poliscyclo
Section: polynomials
C-Name: poliscyclo
Prototype: lG
Help: poliscyclo(f): returns 0 if f is not a cyclotomic polynomial, and n
 > 0 if f = Phi_n, the n-th cyclotomic polynomial.
Doc: returns 0 if $f$ is not a cyclotomic polynomial, and $n > 0$ if $f =
 \Phi_n$, the $n$-th cyclotomic polynomial.
 \bprog
 ? poliscyclo(x^4-x^2+1)
 %1 = 12
 ? polcyclo(12)
 %2 = x^4 - x^2 + 1
 ? poliscyclo(x^4-x^2-1)
 %3 = 0
 @eprog
