原题目： A perfect number is a number for which the sum of its proper divisors is exactly equal to the number. For example, the sum of the proper divisors of 28 would be 1 + 2 + 4 + 7 + 14 = 28, which means that 28 is a perfect number.
A number n is called deficient if the sum of its proper divisors is less than n and it is called abundant if this sum exceeds n.
As 12 is the smallest abundant number, 1 + 2 + 3 + 4 + 6 = 16, the smallest number that can be written as the sum of two abundant numbers is 24. By mathematical analysis, it can be shown that all integers greater than 28123 can be written as the sum of two abundant numbers. However, this upper limit cannot be reduced any further by analysis even though it is known that the greatest number that cannot be expressed as the sum of two abundant numbers is less than this limit.
Find the sum of all the positive integers which cannot be written as the sum of two abundant numbers.
分析： 求出所有的盈数，确定数甲为两个盈数的和，继而求出数甲的和，用总和减去数甲的和即可。 在求出数甲的时候有多种方法，我采用了室友的方法，用for循环寻找小于k的盈数，继而如果k-盈数仍为盈数，即可确定k为数甲。
a=0; b=[]; c=0; d=0; m=0; for i=2:28123 for k=1:i-1 if mod(i,k)==0 a=a+k; end end if a>i b=[b,i]; end a=0; end for k=24:28123 for l=1:length(b) if k>b(l)&&ismember((k-b(l)),b)==1 c=c+k; break end end end for m=m:28123 d=d+m; end sum1=d-c最后输出结果是4179871
