makelist takes as argument a function f,
the bounds a,b of an index variable and a step p
(by default 1 or -1 depending on the bounds order).
makelist makes the list [f(a),f(a+p)...f(a+k*p)] with k such that : a<a+k*p ≤ b <a+(k+1)*p or a>a+k*p ≥ b >a+(k+1)*p.
or first define the function h(x)=x2 by h(x):=x
Warning!!! purge x if x is not symbolic.