The Whitney graph isomorphism theorem gives an example of an extraordinary exception: a very general statement holds except for

onevery specific case.Another example is the classification theorem for finite simple groups: a very general statement holds except for

very few (26)sporadic cases.I am looking for more of

this kindof theorems-with-not-so-many-sporadic-exceptions(

) where the exceptions don’t come in a row and/oradded:

in the beginning – but are scattered truly sporadically.(A late thanks to Asaf!)

**Answer**

Every automorphism of Sn is inner if n≠6.

P.S. That S6 has an `essentially’ unique outer automorphism is quite a non-obvious fact.

**Attribution***Source : Link , Question Author : Community , Answer Author : Community*