求解：PREP07数学破解版 PS1 第七题

prakashliu

7.    905-!-item-!-187;#058&000575

For every positive even integer n, the function h(n) is defined to be the product of all the even integers from 2 to n, inclusive.  If p is the smallest prime factor of h(100) + 1, then p is

(A) between 2 and 10

(B) between 10 and 20

(C) between 20 and 30

(D) between 30 and 40

(E) greater than 40
答案是E
求教！

prakashliu

论坛高手已经解决，复制过来
也可以这么算
H（100）+1=2*（1*2*3*...*50）+1

可以看出2~50里面所有质数都是H（100）的质数因子

加上1之后，2~50之内的质数因子都不是H（100）+1的质数因子了

选e