Print out the n-th entry in the fibonacciSequence series. The
fibonacci series is an ordering of numbers where each number is the
sum of the preceding two. For example, the sequence [0, 1, 1, 2, 3, 5, 8, 13, 21, 34] forms the first ten entries of
the fibonacci sequence.
fibonacci(1) // 1
fibonacci(2) // 1
fibonacci(3) // 2
fibonacci(4) // 3