Factor pair
= Factor pair
A pair of <positive integers> $(a,b)$ with $ab=n$ for a specified <positive integer> $n$. Pairing each <divisor> $a$ with $n/a$ gives $\tau(n)/2$ unordered <factor pairs> for nonsquare $n$, and $(\tau(n)+1)/2$ for a <perfect square>, where $\tau(n)$ is the <divisor function>.