fact: Definition metacyclic A := [exists H : {group gT}, [&& cyclic H, H <| A & cyclic (A / H)]].
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice div) mathcomp(fintype bigop prime finset fingroup morphism) mathcomp(perm automorphism quotient gproduct ssralg) mathcomp(finalg zmodp poly)