Practice By Tag: Counting Functions

1 . Let $n \geq 1$ be an integer. Consider functions $$ f : \{1,2,3,\dots,n\} \rightarrow \{1,2,3,\dots,7n\} $$ such that, for each $i$ with $1 \leq i \leq n$, $f(i)$ is divisible by 7. How many such functions are there?