The a(6) = 4 operations are the two shown below and their converses.
| 1 2 3 4 5 6 | 1 2 3 4 5 6
--+------------ --+------------
1 | 1 2 3 4 5 6 1 | 1 2 3 1 2 3
2 | 1 2 3 4 5 6 2 | 1 2 3 1 2 3
3 | 1 2 3 4 5 6 3 | 1 2 3 1 2 3
4 | 1 2 3 4 5 6 4 | 4 5 6 4 5 6
5 | 1 2 3 4 5 6 5 | 4 5 6 4 5 6
6 | 1 2 3 4 5 6 6 | 4 5 6 4 5 6
(End)
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