derived length 16D70 1 20D10 1 Lie nilpotent ideal 1 \(\pi\)-length,nilpotent \(\pi\)-length 1 \(\pi\)-solvable group 1 \(p\) -length 1 \(p\)-rank 1 associative ring 1 bicyclic group 1 metacyclic group 1 nilpotent lengths 1 one-sided ideal 1 rank 1