4 and 13 make the most sense, but some people (not me) consider 13 to be bad luck, and I don't know if Terry will feel comfortable going to a single digit after having double digits all these years—might leave him feeling unbalanced—so you can't rule out some wacky number up in the 40s, or the first-ever triple zero. Wait, I've got it ...
[(4 x 13) - cos31]/(-7*) - 15** + √34*** =
computing ...
16.47
That one's not retired yet, right?
* the opposite of our last MLE, JO, which should be a good thing
** the approximate angle of a jet at takeoff
*** Terry's age