请教一道Prep MATH

bastencools

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, the 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

fernandchan

h(100)=2*4*6*8*10*.....*100 质因子 1 2 3 5 7 。。。37 都是h(100)的因子

所以这些因子都不是h(100)+1的因子 So p is greater than 40

sweetcorns

精辟！加一点，h(100)的质因子最大为47，所以p 大于40

taohuaxianzi

顺便说一下, 1 不是 prime number, 有时候算 prime number 个数的时候,如果算上它你就亏大拉.

XIAOHANMEIME

QUOTE:

h(100)=2*4*6*8*10*.....*100 质因子 1 2 3 5 7 。。。37 都是h(100)的因子

所以这些因子都不是h(100)+1的因子 So p is greater than 40

还是不明白呀，什么意思啊？怎么加１就不是了？

蓝色的小猫

tip: h(n)+1 prime factors if exist, shall > n/2 (n is a positive even number)