Re: [math-fun] Asimov's group-metric puzzle

On Thu, Sep 17, 2015 at 9:25 PM, Warren D Smith <warren.wds@gmail.com> wrote:

Anyhow, if my search thru the ATLAS to find out which simple groups have outer auts, is not to be largely a waste of time, then we need next to answer: when simple groups are glued together to make more complex groups, what happens to the count of their outer automorphisms?

The answer to this question won't be, well, simple. Consider the fact that A_n has an outer automorphism for n > 3, but S_n, built out of A_n and Z_2, has an outer automorphism only when n = 6. Andy