Restklassenringe (Z)/mod 20/Multiplikationstafel

$\begin{array}{ccccccccccccccccccccc}\cdot & 0& 1& 2& 3& 4& 5& 6& 7& 8& 9& 10& 11& 12& 13& 14& 15& 16& 17& 18& 19\\ 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0& 0\\ 1& 0& 1& 2& 3& 4& 5& 6& 7& 8& 9& 10& 11& 12& 13& 14& 15& 16& 17& 18& 19\\ 2& 0& 2& 4& 6& 8& 10& 12& 14& 16& 18& 0& 2& 4& 6& 8& 10& 12& 14& 16& 18\\ 3& 0& 3& 6& 9& 12& 15& 18& 1& 4& 7& 10& 13& 16& 19& 2& 5& 8& 11& 14& 17\\ 4& 0& 4& 8& 12& 16& 0& 4& 8& 12& 16& 0& 4& 8& 12& 16& 0& 4& 8& 12& 16\\ 5& 0& 5& 10& 15& 0& 5& 10& 15& 0& 5& 10& 15& 0& 5& 10& 15& 0& 5& 10& 15\\ 6& 0& 6& 12& 18& 4& 10& 16& 2& 8& 14& 0& 6& 12& 18& 4& 10& 16& 2& 8& 14\\ 7& 0& 7& 14& 1& 8& 15& 2& 9& 16& 3& 10& 17& 4& 11& 18& 5& 12& 19& 6& 13\\ 8& 0& 8& 16& 4& 12& 0& 8& 16& 4& 12& 0& 8& 16& 4& 12& 0& 8& 16& 4& 12\\ 9& 0& 9& 18& 7& 16& 5& 14& 3& 12& 1& 10& 19& 8& 17& 6& 15& 4& 13& 2& 11\\ 10& 0& 10& 0& 10& 0& 10& 0& 10& 0& 10& 0& 10& 0& 10& 0& 10& 0& 10& 0& 10\\ 11& 0& 11& 2& 13& 4& 15& 6& 17& 8& 19& 10& 1& 12& 3& 14& 5& 16& 7& 18& 9\\ 12& 0& 12& 4& 16& 8& 0& 12& 4& 16& 8& 0& 12& 4& 16& 8& 0& 12& 4& 16& 8\\ 13& 0& 13& 6& 19& 12& 5& 18& 11& 4& 17& 10& 3& 16& 9& 2& 15& 8& 1& 14& 7\\ 14& 0& 14& 8& 2& 16& 10& 4& 18& 12& 6& 0& 14& 8& 2& 16& 10& 4& 18& 12& 6\\ 15& 0& 15& 10& 5& 0& 15& 10& 5& 0& 15& 10& 5& 0& 15& 10& 5& 0& 15& 10& 5\\ 16& 0& 16& 12& 8& 4& 0& 16& 12& 8& 4& 0& 16& 12& 8& 4& 0& 16& 12& 8& 4\\ 17& 0& 17& 14& 11& 8& 5& 2& 19& 16& 13& 10& 7& 4& 1& 18& 15& 12& 9& 6& 3\\ 18& 0& 18& 16& 14& 12& 10& 8& 6& 4& 2& 0& 18& 16& 14& 12& 10& 8& 6& 4& 2\\ 19& 0& 19& 18& 17& 16& 15& 14& 13& 12& 11& 10& 9& 8& 7& 6& 5& 4& 3& 2& 1\end{array}$