If monogram is the right word– all of the letters and numbers are contained in this symbol. (A quick search will find the image as an animated gif which will show you how to find the characters, if you want some help. There are actually a lot of different places to find most of them.)
I’ve been promising myself a tattoo for a while, and this would be a good all purpose symbol that covers pretty much all the bases: every word in the English language, every book ever written or translated, all your favorite quotations, and math too.
