Discovering the Formula for a Repeating Sequence

[SciSteve]

I have to find a formula for the general term of An for this sequence assuming that the pattern follows and continues. (13,3,13,3...)
I don't think there's any straightforward formulas to use for sequences and series' in finding a formula.
My attempt involved finding two numbers that add to 13 and subtract to 3 which is 8 and 5, but what I'm stuck on is inserting the n variable so that the pattern will keep repeating 13,3,13,3..so on. Totally lost on how to do it and it doesn't even seem that hard.

 

[steelphantom]

Try A_n = 8 + 5*(-1)^(n+1).

 

[SciSteve]

figured it out thanks for the tip