Totient of 2^n+1.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =16a(5) =20a(6) =48a(7) =84a(8) =256a(9) =324a(10) =800a(11) =1364a(12) =3840a(13) =5460a(14) =12544a(15) =19800a(16) =65536a(17) =87380a(18) =186624a(19) =349524a(20) =986880a(21) =1365336a(22) =3345408a(23) =5592404a(24) =16515072a(25) =20250000a(26) =52306176a(27) =84768120a(28) =252645120a(29) =351847488