epvector::const_iterator it=seq.begin();
while (it!=seq.end()) {
coeffseq.push_back(combine_ex_with_coeff_to_pair((*it).rest.coeff(s,n),
epvector::const_iterator it=seq.begin();
while (it!=seq.end()) {
coeffseq.push_back(combine_ex_with_coeff_to_pair((*it).rest.coeff(s,n),