[j for i in range(2, 8) for j in range(i*2, 50, i)]
Is equivalent to: for i in range(2, 8): for j in range(i*2, 50, i): print j
http://www.secnetix.de/olli/Python/list_comprehensions.hawk
http://blog.endpoint.com/2014/04/dictionary-comprehensions-in-python.html