Introduction to Group Theory
... Given two groups G1 = {ai } and G2 = {bk }, their outer direct product
is the group G1 × G2 with elements (ai , bk ) and multiplication
(ai , bk ) · (aj , bl ) = (ai aj , bk bl ) ∈ G1 × G2
• Check that the group axioms are satisfied for G1 × G2 .
• Order of Gn is hn (n = 1, 2) ⇒ order of G1 × G2 is ...