n*phi(n)*phi(phi(n)) is a square.

Terms

a(0) =1a(1) =8a(2) =27a(3) =32a(4) =108a(5) =128a(6) =243a(7) =250a(8) =432a(9) =512a(10) =686a(11) =972a(12) =1000a(13) =1331a(14) =1728a(15) =2048a(16) =2187a(17) =2197a(18) =2744a(19) =3375a(20) =3888a(21) =4000a(22) =5324a(23) =6174a(24) =6250a(25) =6912a(26) =8192a(27) =8748a(28) =8788a(29) =9826