characteristic prime factor cpf(n) is altered from historical prime factor hpf(n). hpf(n) is defined as the prime factor of $n$ that has not appeared for the longest time in $hpf(1)..hpf(n-1)$.
hpf(n) selects the most recently unoccurring prime factor of $n$.
特征素因子 cpf(n) 是从历史素因子 hpf(n) 更改而来。