Background
The Fibonacci sequence is a well-known mathematical series of numbers that has fascinated mathematicians and scientists for centuries. It is a sequence of numbers where each number in the sequence is the sum of the two preceding numbers. The sequence starts with 0, 1, and each subsequent number is the sum of the previous two numbers.
The sequence goes 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on.
Task
Define a function fibonacci that takes one parameter:
When called, the function should return the corresponding fibonacci sequence number (starting from 0).
Caveats:
- The function should be recursive.