a(n) = Sum_{d divides n} phi(d)*phi(n/d).

Terms

a(0) =1a(1) =2a(2) =4a(3) =5a(4) =8a(5) =8a(6) =12a(7) =12a(8) =16a(9) =16a(10) =20a(11) =20a(12) =24a(13) =24a(14) =32a(15) =28a(16) =32a(17) =32a(18) =36a(19) =40a(20) =48a(21) =40a(22) =44a(23) =48a(24) =56a(25) =48a(26) =60a(27) =60a(28) =56a(29) =64