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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.
+;;;;
+
+(load "utils.scm")
+
+(define +top+ 4000000)
+
+(define fib
+  (lambda (n)
+    (case n
+      ((0) 1)
+      ((1) 1)
+      (else (+ (fib (- n 1))
+               (fib (- n 2)))))))
+
+(define result
+  (sum
+    (filter (lambda (x) (= 0 (modulo x 2)))
+            (do ((x 1 (+ x 1))
+                 (f 1 (fib x))
+                 (fs '()))
+              ((>= f +top+) fs)
+              (set! fs (cons f fs))))))
+
+(display result)