Function: sumdivmult
Section: sums
C-Name: sumdivmultexpr
Prototype: GVE
Help: sumdivmult(n,d,expr): sum of multiplicative function expr,
 d running over the divisors of n.
Doc: sum of \emph{multiplicative} expression \var{expr} over the positive
 divisors $d$ of $n$. Assume that \var{expr} evaluates to $f(d)$
 where $f$ is multiplicative: $f(1) = 1$ and $f(ab) = f(a)f(b)$ for coprime
 $a$ and $b$.
 %\syn{NO}
