Whaddaya get when you take one green alien and add one power ring? Why, The Green Lantern, of course! This is simple arithmetic, guys, and probably the most famous equation in history (aside from that whole e=mc² jibber-jabber). A rough replica of this shirt can currently (at the time of writing this, at least) be purchased from Aliexpress.com by clicking here.
Featured on The Big Bang Theory episodes
S05 E23: "The Launch Acceleration"
S06 E16: "The Tangible Affection Proof"
S07 E07: "The Proton Displacement"