# Factorial Symmetry

**Number Theory**Level 3

\[ \large a! b! = a! + b!\]

Let all the pairs of positive integer solutions of \((a,b) \) satisfying the equation above be \((a_1, b_1) , (a_2, b_2) , \ldots , (a_n , b_n) \). Find \[ (a_1 + b_1) + (a_2 + b_2) + \cdots + (a_n + b_n) . \]

\[\]**Notation**: \(!\) denotes the factorial notation. For example, \(8! = 1\times2\times3\times\cdots\times8 \).