4Clojure: For the Win

(for [x (range 40)
    :when (= 1 (rem x 4))]
    x)

x is assigned the range of integer values from 0-39. x is finite so the for stops evaluating when x is fully consumed.
On each iteration the remainder of x/4 is compared to 1 and if they are equal the body is evaluated (which is just x).

(for [x (iterate #(+ 4 %) 0)
    :let [z (inc x)]
    :while (< z 40)]
    z)

x is assigned a lazy sequence of all the multiples of 4 (iterate from 0 applying +4 at each step using an anonymous function). x is infinite so the for is terminated with :while
Each iteration of the for symbol z is assigned x+1.
While z is less than 40 the body is evaluated (which is just z) and the for loop terminates when z >= 40.

(for [[x y] (partition 2 (range 20))]
    (+ x y))

The range from 0-20 is split into segments of 2 numbers. One segment deconstructed into x and y per iteration of the for. The sequence is finite so the for terminates when the full sequence is consumed.
x and y are added as the body of the for.

Each of these results in the same output (a list of each multiple of 4 incremented by 1 up to 37) just by a different mechanism. For my money the first option is probably the best combination of concise and obvious.