σ function


Given a positive integer n, the sum of the integers 0<dn such that d|n is the value of the sum of divisors function for n, often symbolized by a Greek lowercase σ. Thus,

σ(n)=d|nd.

Sometimes this functionMathworldPlanetmath is referred to as σ1(n), highlighting its relation to the divisor functionDlmfDlmfMathworldPlanetmath.

Given coprime integers m and n (that is, gcd(m,n)=1) then σ(mn)=σ(m)σ(n), meaning that the sum of divisors function is a multiplicative functionMathworldPlanetmath.

Title σ function
Canonical name sigmaFunction
Date of creation 2013-03-22 16:07:12
Last modified on 2013-03-22 16:07:12
Owner CompositeFan (12809)
Last modified by CompositeFan (12809)
Numerical id 8
Author CompositeFan (12809)
Entry type Definition
Classification msc 11A25
Synonym divisor sigma
Synonym sum of divisors function
Synonym σ1 function