  C. Andre and N. Yan introduced the idea of a supercharacter theory to give a
tractable substitute for character theory in wild groups such as the unipotent
uppertriangular group $U_n(F_q)$. In this theory superclasses are certain
unions of conjugacy classes, and supercharacters are a set of characters which
are constant on superclasses. This paper gives a character formula for a
supercharacter evaluated at a superclass for pattern groups and more generally
for algebra groups.
