euske may be using one of the operating systems (one such being mentioned on this very page) where there is no seq utility.

    JdeBP ~ $seq
    ksh: seq: not found
    JdeBP ~ $

Of course, on the one mentioned there is jot.

And on bash you can simply use {1..n}:

    $ echo {1..5}
    1 2 3 4 5

If you have Bash 4.0 or above, you can include a step size:

    $ echo {1..10..2}
    1 3 5 7 9