The number 13 is not used in Formula 1.
Haha, the funny thing is I knew that because on Friday the 13th the Chinese FP1 was on, and someone mentioned that there was no car number 13 because they think it's bad luck XDI didn't know that.
Thanks
But you know, it's a bid of a ridiculous thing. I'm wondering if Kobayashi would be willing to drive the number 4 car.