# Factoring expression involving exponentials

I've got a complicated expression, which looks like: e(4ik+3iω+ip)−e(4ik+2iω+2ip)−e(4ik+2iω)+e(4ik+iω+ip)+2e(2ik+4iω+ip)−e(2ik+3iω+2ip)−e(2ik+3iω) + ...

How would you do to factor the exponentials with the same power of k, i.e. e(4ik)*(...) + e(2ik)*(...) and so on?