15B33 15A30 commutative ring similarity 15A21 2-monomial matrix 22D20 94B05 Golay codes Jacobson radical canonically \(t\)-cyclic matrix codes over fields defining sequence equivalent matrices modulo an ideal extended binary codes free module group group algebra hereditary reducible matrix indecomposable matrix irreducible matrix linear operator local ring perfect \((I,J)\)-matrix prime element representation self-dual codes wildness