Move to group.subnormal series
Since this is a property of abstract groups, maybe move this to group.subnormal_series and edit group.solvable to refer to it.
The L-functions and modular forms database: Move to group.subnormal seriesmathswitch — infrastructure for relaying and exchanging mathematical concepts
Since this is a property of abstract groups, maybe move this to group.subnormal_series and edit group.solvable to refer to it.
The L-functions and modular forms database: Move to group.subnormal series