J-13? Chinese? it doesn't belong in the list anyway. But the X-13 was the Ryan Vertijet...it never succeeded to become a fighter, probably because of the number 13
F-19 was skipped on request by Lockheed, they wanted to introduce the F-5 derivative (now F-20) and since it was intended as export fighter, they didn't an odd number because the soviet fighters used odd numbers.