gcd too slow for large degree univariate poly
CoCoA-5 used more than 6Gbytes of memory while trying to compute
f := x^15 +x^14 +x^13 +x^12 -x^11 -x^10 -x^7 -x^6 -x^3 +x^2 +x +1
Why so much memory? Was it using a dense representation?