Prove that $16 ^ {2023} + 1$ is divisible by $17 ^ 2$.
Prove that $16 ^ {2023} + 1$ is divisible by $17 ^ 2$.
It is clear that $16 ^ {2023} + 1$ is divisible by $17$, but why it is divisible by $17 ^ 2$ is not clear.
The hint.
Use $2023=7\cdot17^2$, $16=17-1$ and the binomial of Newton.
Now we see that $16^{2023}+1$ is divisible even by $17^3$.