区间(a, b)内，与(p_m)#既约的自然数个数

设素数连乘积 p_m# = 2*3*5*...*p_m = M
区间（a,b）内，至少有一个与 p_m# 既约的自然数，则
b∏(1-1/p) - a∏(1-1/p) = (b-a)∏(1-1/p) > 1,
2 ≤ p ≤ p_m
b-a > 1 / ∏(1-1/p) = ∏[p/(p-1)]
.
实例验证：
p_m = 5，b-a > 2*3*5 / 1*2*4 = 30/8 = 3.75
p_m = 7，b-a > 2*3*5*7 / 1*2*4*6 = 210/48 = 4.375
p_m = 11，b-a > 2*3*5*7*11 / 1*2*4*6*10 = 2310/480 = 4.8125

p_m = 7，L(m) ≤ p_(m-3) + 2*p_(m-2) + 1 = 2 + 2*3 + 1 = 9
p_m=11，L(m) ≤ p_(m-3) + 2*p_(m-2) + 1 = 3 + 2*5 + 1 = 1
p_m=13，L(m) ≤ p_(m-3) + 2*p_(m-2) + a = 5 + 2*7 + 3 = 22
p_m=17，L(m) ≤ p_(m-3) + 2*p_(m-2) + 1 = 7 + 2*11 + 1 = 30
p_m=19，L(m) ≤ p_(m-3) + 2*p_(m-2) + 3 = 11 + 2*13 + 3 = 40
p_m=23，L(m) ≤ p_(m-3) + 2*p_(m-2) + 3 = 13 + 2*17 + 3 = 50
p_m=29，L(m) ≤ p_(m-3) + 2*p_(m-2) + 3 = 17 + 2*19 + 3 = 58
p_m=31，L(m) ≤ p_(m-3) + 2*p_(m-2) + 1 = 19 + 2*23 + 1 = 66
p_m=37，L(m) ≤ p_(m-3) + 2*p_(m-2) + 1 = 23 + 2*29 + 1 = 82
p_m=41，L(m) ≤ p_(m-3) + 2*p_(m-2) + 5 = 29 + 2*31 + 5 = 96
p_m=43，L(m) ≤ p_(m-3) + 2*p_(m-2) + 5 = 31 + 2*37 + 5 = 110