选择题
2007 AMC 8 Problem 10: Nested Factor-Sum Function
For any positive integer n, define [n] to be the sum of the positive factors of n. For example, [6] = 1 + 2 + 3 + 6 = 12. Find [[11]].
A.
13
B.
20
C.
24
D.
28
E.
30