-- Fibonacci number -- source: https://wiki.haskell.org/The_Fibonacci_sequence#Using_the_infinite_list_of_Fibonacci_numbers fibonacci_nums = 0 : 1 : zipWith (+) fibonacci_nums (tail fibonacci_nums) fib = (!!) fibonacci_nums main = print $ fib 70000 -- the fibonacci_nums can be write as: -- fibonacci_nums = 0 : 1 : [x+y | ~(x,y) <- zip fibonacci_nums (tail fibonacci_nums)]