Reference: fibonacci
fibonacci(n) returns the nth Fibonacci number. fibonacci(0) = 0, fibonacci(1) = 1, fibonacci(2) = 1, fibonacci(n) = fibonacci(n − 1) + fibonacci(n − 2).
fibonacci(n) returns the nth Fibonacci number. fibonacci(0) = 0, fibonacci(1) = 1, fibonacci(2) = 1, fibonacci(n) = fibonacci(n − 1) + fibonacci(n − 2).