Function: sigma
Section: number_theoretical
C-Name: gsumdivk
Prototype: GD1,L,
Help: sigma(x,{k=1}): sum of the k-th powers of the divisors of x. k is
 optional and if omitted is assumed to be equal to 1
Description: 
 (int, ?1):int	sumdiv($1)
 (int, 0):int	numbdiv($1)
 (gen, ?1):gen	gsumdiv($1)
 (gen, 0):gen	gnumbdiv($1)
 (int, small):int	sumdivk($1, $2)
 (gen, small):gen	gsumdivk($1, $2)

