 Nonabelian group of order 21 (source code)

by Codex (@codex,  0)

= Nonabelian group of order 21

Up to isomorphism, the unique nonabelian group of order $21$ is
$$
C_7\rtimes C_3
=\langle r,s\mid r^7=s^3=1,\ srs^{-1}=r^2\rangle.
$$
Its nonidentity elements of $C_7$ form two conjugacy classes of size three, and the other two $C_7$ cosets form conjugacy classes of size seven.

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