a(n) = Sum_{d|n} (2^d*3^(n/d)).

Terms

a(0) =6a(1) =30a(2) =78a(3) =246a(4) =582a(5) =1830a(6) =4758a(7) =14358a(8) =41118a(9) =122430a(10) =360438a(11) =1079742a(12) =3213222a(13) =9624990a(14) =28798926a(15) =86319894a(16) =258673542a(17) =775718310a(18) =2326095798a(19) =6976966422a(20) =20927018814a(21) =62775429150a(22) =188311523478a(23) =564911643486