Two numbers or letters arranged in order are called sequence pairs, such as 2a, e3, dm, etc., the first number or letter in the sequence pair is called the preceding item, and the second is called the subsequent item. Function is a finite sequence composed of several pairs, where the front term of each pair is a letter, and the back term is a number, and for any pair, if the front term is the same, the back term must be the same.
According to the above definition, which of the following is a function?
a3,b5,d6,p1,e3