Dirichlet convolution of powers of 3 (3,9,27,...) with themselves.

Terms

a(0) =9a(1) =54a(2) =162a(3) =567a(4) =1458a(5) =4860a(6) =13122a(7) =40824a(8) =118827a(9) =358668a(10) =1062882a(11) =3206142a(12) =9565938a(13) =28737180a(14) =86106564a(15) =258404985a(16) =774840978a(17) =2324916594a(18) =6973568802a(19) =20921808654a(20) =62762237316a(21) =188289546300a(22) =564859072962