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?
import Control.Arrow fib = :1:[i+j|(i,j)<-zip fib $tail fib] p025 = length.takeWhile((<1000).snd).map(id&&&length.show)$ fib
fib = :1:[i+j|(i,j)<-zip fib $tail fib] p025 = length.takeWhile(<1000).map(length.show)$ fib