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tzach/even_fibonacci_numbers.clj

Created August 18, 2015 09:36
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even_fibonacci_numbers.clj
# Even Fibonacci numbers
# https://projecteuler.net/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.
(defn fib
([] (fib 1))
([a] (fib 1 a))
([a b]
(cons a (lazy-seq (fib b (+ a b))))))
(->> (fib) (take-while #(< % 4000000)) (filter even?) (apply +))
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