Highest proper factor of n!+1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =5a(5) =11a(6) =103a(7) =71a(8) =661a(9) =19099a(10) =329891a(11) =1a(12) =36846277a(13) =75024347a(14) =3790360487a(15) =22163972339a(17) =538105034941a(20) =117876683047