Dirichlet convolution of 3^(n-1) with phi(n).

Terms

a(0) =1a(1) =4a(2) =11a(3) =32a(4) =85a(5) =260a(6) =735a(7) =2224a(8) =6585a(9) =19780a(10) =59059a(11) =177472a(12) =531453a(13) =1595076a(14) =4783175a(15) =14351168a(16) =43046737a(17) =129147252a(18) =387420507a(19) =1162281440a(20) =3486785925a(21) =10460412292a(22) =31381059631a(23) =94143360944a(24) =282429536825a(25) =847289140932