Superabundant Numbers
一个有意思的问题,也是Knuth出的。
The abundance of an integer n is the sum of the divisors of n (including n itself), divided
by n. Integer n is k-abundant if its abundance is at least k.
For example, the sum of the divisors of 6 is 6+3+2+1=12, and 12/6=2, so 6 is 2-abundant.
As another example, the sum of the divisors of 120 is
120+60+40+30+24+20+15+12+10+8+6+5+4+3+2+1=360
so 120 is 3-abundant. It happens that 6 is the smallest 2-abundant number and 120 is the smallest
3-abundant number. They happen to be exactly 2- and 3-abundant, respectively, but it is generally
possible that the smallest k-abundant number has abundance greater than k.
The task is to write a program that finds the smallest k-abundant number for k=1,2,..
How high can you go?