FibonacciLib.sol

// library contract - calculates fibonacci-like numbers;
contract FibonacciLib {
    // initializing the standard fibonacci sequence;
    uint public start;
    uint public calculatedFibNumber;
    // modify the zeroth number in the sequence
    function setStart(uint _start) public {
        start = _start;
    }
    function setFibonacci(uint n) public {
        calculatedFibNumber = fibonacci(n);
    }
    function fibonacci(uint n) internal returns (uint) {
        if (n == 0) return start;
        else if (n == 1) return start + 1;
        else return fibonacci(n - 1) + fibonacci(n - 2);
    }
}