Created
May 1, 2010 03:38
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; 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, ... | |
; Find the sum of all the even-valued terms in the sequence which do not exceed four million. | |
(defun calc-next (a b) (+ a b)) | |
(defun multiple-of (x y) (= 0 (rem x y))) | |
(let ((answer 2) (a 1) (b 2) n) | |
(loop while (< b 4000000) do | |
(setf n (calc-next a b)) | |
(when (multiple-of n 2) (setf answer (+ answer n))) | |
(setf a b) | |
(setf b n)) | |
(print answer)) |
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