How do I find a function in this sequence: -4, -7, -9, -10, -10, -9, -7, -4, 0, 5, 11, 18?

The function has to equal to all the numbers in the seguence or:The function has to equal to all the numbers in the seguence

The function has to equal to all the numbers in the seguence

or:The function has to equal to all the numbers in the seguence

Tags:sequence,