a | b conditional π π {\displaystyle{\displaystyle a|b}} a β£ b conditional π π {\displaystyle{\displaystyle a\mid b}} 2 β’ n !! 2 double-factorial π {\displaystyle{\displaystyle 2n!!}} s β’ d β’ a β’ f β’ j β’ k β’ l β’ s β’ d β’ a β’ f π π π π π π π π π π π {\displaystyle{\displaystyle sdafjklsdaf}}