How can I  make a `Tribonacci` sequence that is in listing form? it suppose to look like the `Fibonacci` sequence but I couldn't get the same result with `Tribonacci`.[![enter image description here][1]][1]

    Array[Fibonacci, 9]
    
>     {1, 1, 2, 3, 5, 8, 13, 21, 34}
    
    Array[Tribonacci, 9]
    
>     {Tribonacci[1], Tribonacci[2], Tribonacci[3], Tribonacci[4], 
     Tribonacci[5], Tribonacci[6], Tribonacci[7], Tribonacci[8], Tribonacci[9]}


  [1]: http://i.stack.imgur.com/qcumA.png