对于正整数n,设φ(n)和σ(n)分别是n的Euler数和约数之和,当n| φ(n)+σ(n)时,n称为Nicol数.运用初等方法讨论了Nicol数的存在性,设a=pα1 pα22 …pαrr,其中r是大于1的正整数,pi(i=1,2,…,r)是不同的奇素数,αi(i=1,2,…,r)是正奇数,证明了如果n=a或2a,则n不是Nicol数.
For any positive integer n,let φ(n) and σ(n) denote the Euler function and the sum of divisors of n respectively.If n |φ(n)+σ(n),then n is called a Nicol number.In this paper,using elementary methods,the existence of Nicol numbers is discussed.Let a =pα11pα22 … pαrr,where r is a positive integer withr> 1,pi (i =1,2,…,r) are distinct odd primes and αi (i =1,2,…,r) are positive odd integers,and if n =a or2a,it can be proved than n is not a Nicol number.