Suppose i have a `a = range(1,51)`. How can i slice `a` to create a new list that look like this:

```
[1,2,3,11,12,13,21,22,23,31,32,33,41,42,43]

```

Is there a pythonic way that can help me do this without writing function?

I know that `[start:stop:step`] for periodically slicing one element but i'm not sure if i'm missing something obvious.

EDIT: The suggested duplicate question/answer is not the same as mine question. I simply asked to slice/extract periodically elements from a larger list/array. The suggested duplicate modifies elements of existing array.