No account of the symmetric group can be complete without mentioning the remarkable fact that the symmetric group of degree n (finite or infinite) has an outer automorphism if and only if n=6. Here are the definitions. An automorphism of a group G is a permutation p of the group which preserves products, that is,…
J. Leskovec, J. Kleinberg, и C. Faloutsos. KDD '05: Proceeding of the eleventh ACM SIGKDD international conference on Knowledge discovery in data mining, стр. 177--187. New York, NY, USA, ACM Press, (2005)