examples of outer automorphism group
It is easy to understand that , since is abelian and there are no inner-automorphisms, save the trivial one.
Also, it is known that
Another example is that, at least for orientable surfaces, the extended mapping class group (or the zeroth homeotopy group) of a surface is related to its fundamental group
via .
References
1. L. K. Hua, I Reiner Automorphisms of unimodular group
, Trans Amer. Math. Soc. 71 (1951), 331-348.
2. H. Zieschang, E. Vogt, H. D. Coldewey, Surfaces and planar discontinuous groups, L.N.M. 875 (1981) Springer-Verlag.