还需要考虑溢出等问题，闲来无事写了写

Func
     
       a = (arg1, arg2) => 0f;//initvar depth = 8;a = (lastNumber, currentNumber) =>    {        if (depth <= 0) return currentNumber;        depth--;        return a(currentNumber, currentNumber + lastNumber);    };var result = a(0, 1);