You could shave off a precious few characters using the function reader syntax: (defn euler1 [n] (reduce + (filter #(or (div-by 3 %) (div-by 5 %)))) (range

You could shave off a precious few characters using the function reader syntax: (defn euler1 [n] (reduce + (filter #(or (div-by 3 %) (div-by 5 %)))) (range n))) Or if you're into comprehensions: (defn euler1 [n] (reduce + (for [x (range n) :when (or (div-by 3 x) (div-by 5 x))] x)))