Input is sequence of integers from vocabulary of size `voc_size`

.
Returns vector of integers corresponding to n-gram encoding.
Integers greater than `voc_size`

get encoded as `voc_size^n + 1`

.

## Examples

```
int_to_n_gram(int_seq = c(1,1,2,4,4), n = 2, voc_size = 4)
#> [1] 1 2 8 16
```