Shell script to make directories, subdirectories and files following a pattern

Is it possible to create a script that will create the following structure after running it:

/test/1/1 -> A
/test/1/2 -> B
/test/1/3 -> C
/test/1/4 -> D
/test/1/5 -> E
/test/1/6 -> F
/test/1/7 -> G
/test/1/8 -> H
/test/1/9 -> I
/test/1/10 -> J 
/test/1/11 -> K
/test/1/12 -> L
/test/1/13 -> M
/test/1/14 -> N
/test/1/15 -> O
/test/2/1 -> P
/test/2/2 -> Q
/test/2/3 -> R
/test/2/4 -> S
/test/2/5 -> T
/test/2/6 -> U
/test/2/7 -> V
/test/2/8 -> X
/test/2/9 -> Y
/test/2/10 -> Z
/test/2/11 -> A
/test/2/12 -> B
/test/2/13 -> C
/test/2/14 -> D
/test/2/15 -> E
/test/3/1 -> F
/test/3/2 -> G
/test/3/3 -> H
.........
/test/10/15 -> ???

As you can see, in this example, the directory "test" is the parent directory and the numbered ones are subdirectories. The letters are files, not folders. Each time the alphabet ends, it will start from the beginning in the next directory.

How can I create a script that will make this easier rather than just creating them manually?