a(1) = 1; a(n) = Sum_{d|n, d < n} phi(n/d) * a(d)^2.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =8a(6) =6a(7) =15a(8) =14a(9) =24a(10) =10a(11) =96a(12) =12a(13) =48a(14) =56a(15) =255a(16) =16a(17) =344a(18) =18a(19) =656a(20) =108a(21) =120a(22) =22a(23) =9840a(24) =84a(25) =168a(26) =434a(27) =2448a(28) =28a(29) =4608