im trying to make a regular expression rule that targets file names with 13 characters that has a mixture of a-z letters and 0-9 numbers specifically, but allows everything else including file names with 13 characters that do NOT have a mixture of a-z letters and 0-9 numbers (IE file name with ALL 0-9 numbers or ALL a-z letters can pass just not a mix of the two). ive been fiddling around with auto generators and managed to figure out thats what i was going for in particular but i figure i would ask since last time anon helped me with a great bit im still using.

ill post a wholesome picture in return. i was thinking a snake but if you make it for me you can pick.