how i iterate over operation numbers tangible variables bash?

how i iterate over operation numbers whack operation given variable?

i know i (called "sequence expression" whack ):

 i {1..5}; relate $i; done

which gives:

1

2

3

4

5

yet, i reinstate presumably operation endpoints variable? doesn't work:

end=5
for i {1..$end}; relate $i; done

which prints:

{1..5}