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

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =4a(5) =12a(6) =6a(7) =24a(8) =18a(9) =32a(10) =10a(11) =124a(12) =12a(13) =60a(14) =72a(15) =240a(16) =16a(17) =336a(18) =18a(19) =440a(20) =132a(21) =140a(22) =22a(23) =2088a(24) =100a(25) =192a(26) =378a(27) =1044a(28) =28a(29) =2096