Positive divisors of integer n in increasing order:
abjad> from abjad.tools import mathtools
abjad> mathtools.divisors(84)
[1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, 84]
abjad> for x in range(10, 20):
... print x, mathtools.divisors(x)
...
10 [1, 2, 5, 10]
11 [1, 11]
12 [1, 2, 3, 4, 6, 12]
13 [1, 13]
14 [1, 2, 7, 14]
15 [1, 3, 5, 15]
16 [1, 2, 4, 8, 16]
17 [1, 17]
18 [1, 2, 3, 6, 9, 18]
19 [1, 19]
Allow nonpositive n:
abjad> mathtools.divisors(-27)
[1, 3, 9, 27]
Raise type error on noninteger n.
Raise not implemented error on 0.
Return list of positive integers.