Problem 618
Numbers with a given prime factor sum
Consider the numbers 15, 16 and 18:
15, 16 and 18 are the only numbers that have 8 as sum of the prime factors (counted with multiplicity).
We define
Hence
Other examples:
The Fibonacci sequence is
Find the last nine digits of
给定质因数和的整数
考虑整数15,16和18的质因数分解:
15,16和18是仅有的质因数和(包括重复)为8的整数。
记
因此
其它例子包括:
考虑斐波那契数列
求
Gitalking ...