480 Representations of Octonions from Cayley-Dickson
The extension of the "righthanded" quaternions e12 = e22 = e32 = e1e2e3 = -1 by the Cayley-Dickson construction using the "canonical" mapping (i.e. ei ↔ (ei, 0) for i = 1,2,3; e4 ↔ (0, 1); ei+4 ↔ (0, ei)) gives one specific representation of the octonions ("XOR/6e") out of 480 possible representations:
| e0 | e1 | e2 | e3 | e4 | e5 | e6 | e7 |
e0 | e0 | e1 | e2 | e3 | e4 | e5 | e6 | e7 |
e1 | e1 | -e0 | e3 | -e2 | -e5 | e4 | -e7 | e6 |
e2 | e2 | -e3 | -e0 | e1 | -e6 | e7 | e4 | -e5 |
e3 | e3 | e2 | -e1 | -e0 | -e7 | -e6 | e5 | e4 |
e4 | e4 | e5 | e6 | e7 | -e0 | -e1 | -e2 | -e3 |
e5 | e5 | -e4 | -e7 | e6 | e1 | -e0 | -e3 | e2 |
e6 | e6 | e7 | -e4 | -e5 | e2 | e3 | -e0 | -e1 |
e7 | e7 | -e6 | e5 | -e4 | e3 | -e2 | e1 | -e0 |
All other representations can be generated by appropriate deviations from the canonical mapping. There are 24*4! ways of mapping (0,1) and (0,ei) i=1,2,3 to the new appended imaginaries ±eJ J=4,5,6,7. Any resulting multiplication table can in fact be obtained by 8 different such mappings, e.g. the mappings listed in the following columns all generate the same multiplication table as the canonical mapping (1st column of the table):
(0, 1) | e4 | -e4 | e5 | -e5 | e6 | -e6 | e7 | -e7 |
(0, e1) | e5 | -e5 | -e4 | e4 | e7 | -e7 | -e6 | e6 |
(0, e2) | e6 | -e6 | -e7 | e7 | -e4 | e4 | e5 | -e5 |
(0, e3) | e7 | -e7 | e6 | -e6 | -e5 | e5 | -e4 | e4 |
Permutations among the 4 new imaginaries of the canonical mapping thus produce 2*4! = 48 different multiplication tables containing the quaternion multiplication table for (e1,e2,e3) in the upper left corner, i.e. 48 Cayley-Dickson extensions of e12 = e22 = e32 = e1e2e3 = -1. This is doubled by considering the left-handed version e12 = e22 = e32 = -1 with e1e2e3 = 1. There are also 4 other possible triads containing e1 and e2 (i.e. (e1,e2,ek) k=4,5,6,7), each with right- and left-handed versions. Thus, there are 10 possible distinct quaternionic multiplication tables in the upper left corner, each extended in 48 ways by Cayley-Dickson and permutation of the new imaginaries, bringing the total to 480.