), ▁order ▁ 2 4 , ▁( D u ▁Val ▁# 2 6 b " ▁( O / C 1 ; O / C 1 ), ▁Con way ▁+ 1 / 2 4 [ O × ]). ▁An ▁example ▁is ▁the ▁sn ub ▁t etra hed ral ▁anti pr ism , ▁, ▁although ▁it ▁can ▁not ▁be ▁made ▁uniform . ▁ ▁The ▁ion ic ▁subgroup ▁is ▁[( 3 , 3 )+ , 2 ], ▁( ), ▁order ▁ 2 4 , ▁( D u ▁Val ▁# 3 9 b ' ▁( T / C 1 ; T / C 1 ) c *, ▁Con way ▁+ 1 / 1 2 [ T × ]. 2 3 ). ▁An ▁example ▁is ▁the ▁sn ub ▁t etra hed ral ▁pr ism , ▁. ▁ ▁The ▁half ▁subgroup ▁is ▁[ 3 , 3 , 2 , 1 + ] ▁= ▁[ 3 , 3 , 1 ] ▁= ▁[ 3 , 3 ], ▁( ▁= ▁), ▁order ▁ 2 4 , ▁( D u ▁Val ▁# 3 9 b " ▁( T / C 1 ; T / C 1 ) − *, ▁Con way ▁+ 1 / 1 2 [ T × ]. 2 1 ). ▁It ▁is ▁called ▁the ▁t etra hed ral ▁py ram idal ▁group ▁and ▁is ▁the ▁ 3 D ▁t etra hed ral ▁group , ▁[ 3 , 3 ]. ▁ ▁A ▁regular ▁t etra hed ral ▁py ram id ▁can ▁have ▁this ▁symmetry , ▁with ▁Sch lä fli ▁symbol