A notation for large numbers defined by Steinhaus. In this notation, n inside a triangle denotes n^n, n inside a box denotes "n in n triangles, " and n inside a circle denotes "n in n squares." A modified version due to Moser eliminates the circle notation, continuing instead with polygons of ever increasing size, so n in a pentagon is n with n squares around it, etc.

circle notation | large number | mega | Moser