# §27.1 Special Notation

(For other notation see Notation for the Special Functions.)

$d,k,m,n$ positive integers (unless otherwise indicated). $d$ divides $n$. greatest common divisor of $m,n$. If $\left(m,n\right)=1$, $m$ and $n$ are called relatively prime, or coprime. greatest common divisor of $d_{1},\dots,d_{n}$. sum, product taken over divisors of $n$. sum taken over $m$, $1\leq m\leq n$ and $m$ relatively prime to $n$. prime numbers (or primes): integers ($>1$) with only two positive integer divisors, $1$ and the number itself. sum, product extended over all primes. real numbers. $\sum_{n=1}^{\left\lfloor x\right\rfloor}$. natural logarithm of $x$, written as $\mathop{\ln\/}\nolimits x$ in other chapters. Riemann zeta function; see §25.2(i). Jacobi symbol; see §27.9. Legendre symbol; see §27.9.