; 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.
(defn next-fib-num [seq]
  (reduce + (take-last 2 seq)))
(defn fib-seq-to [max]
  (loop [seq [1 2]]
    (if (>= (last seq) max)
      (butlast seq)
      (recur (conj seq (next-fib-num seq))))))
(println (reduce + (filter even? (fib-seq-to 4000000))))

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