Problem 25

Problem 25
Filename: prob25.hs

-- Prob 25
-- The Fibonacci sequence is defined by the recurrence relation:
-- 
-- Fn = Fn1 + Fn2, where F1 = 1 and F2 = 1.
-- Hence the first 12 terms will be:
-- 
-- F1 = 1
-- F2 = 1
-- F3 = 2
-- F4 = 3
-- F5 = 5
-- F6 = 8
-- F7 = 13
-- F8 = 21
-- F9 = 34
-- F10 = 55
-- F11 = 89
-- F12 = 144
-- The 12th term, F12, is the first term to contain three digits.
-- 
-- What is the first term in the Fibonacci sequence to contain 1000 digits?
 

module Prob25
    where
      number = 1000
      fibs = 0 : 1: [a+b | (a,b) <- zip fibs (tail fibs)]
      answer = length((takeWhile (<number) (map (length . show) fibs)))

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