I counted 61 aircraft that used the number 13 in their designation (in its "pure" form without additional digits - for example, F13C or 13-A, designations with numbers like 113, 213 or 131 were not included).
The list contains 47 airplanes, 4 helicopters (+gyroplanes), and 10 (motor) gliders that were at least finished in construction, airplanes remained in the projects only were not included.
The designations H-13/OH-13/UH-13 or CL-13/-13A/-13B for modifications were treated as one.
The designation containing the number 13 may not have been the only designation assigned to a given aircraft, but it was to be used officially. There is at least one case where such a designation was a myth.
Another 7 aircraft had the number 13 in Roman numerals (XIII) in the designation.