Autofill Overlapping Averages

Hello!

I feel like I'm missing something simple here. I want to average every thirteen rows, with one row of overlap. The formula below lets me average every thirteen rows, but I can't figure out how to add overlap.

=AVERAGE(OFFSET($B$14,(ROW()-ROW($AB$44))*13,,13))

For example, I want to average B14-26, then B26-38, then B38-50, and so on. Can anyone help?
Thank you!