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+;;;;
+;; Even Fibonacci numbers
+;; Problem 2
+;;
+;; Each new term in the Fibonacci sequence is generated by adding the previous two terms. By
+;; starting with 1 and 2, the first 10 terms will be:
+;; 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
+;; By considering the terms in the Fibonacci sequence whose values do not exceed four
+;; million, find the sum of the even-valued terms.
+;;;;
+
+(def fib
+  (memoize (fn [n]
+             (case n
+               0 1
+               1 1
+               (+' (fib (-' n 1)) (fib (-' n 2)))))))
+
+(def +top+ 4000000)
+
+(def result
+  (reduce +
+    (for [x (range 1 1000)
+          :let [f (fib x)]
+          :when (= (mod f 2) 0)
+          :while (< f +top+)]
+      f)))
+
+(println result)