number theory - Generate unique integer from $n$ integers and solve to get the integers from result

What could be the best way to generate a unique integer from $n$ integers in order $(n_1,n_2,\ldots)$?

Further, from $n$, we should be able to get back each $n_1, n_2,\ldots $ etc.
For example, from $n_1=120, n_2=135, n_3=789, n_4=980$, we need a number $n$. And from $n$, we should be able to get back numbers $n_1=120, n_2=135, n_3=789, n_4=980$. For the sake of computation effort, it would be better if we could generate as much small number as possible.

Thank you.