a(n) = 3*n*(2^n - 1).

Terms

a(0) =0a(1) =3a(2) =18a(3) =63a(4) =180a(5) =465a(6) =1134a(7) =2667a(8) =6120a(9) =13797a(10) =30690a(11) =67551a(12) =147420a(13) =319449a(14) =688086a(15) =1474515a(16) =3145680a(17) =6684621a(18) =14155722a(19) =29884359a(20) =62914500a(21) =132120513a(22) =276823998a(23) =578813883a(24) =1207959480a(25) =2516582325a(26) =5234491314a(27) =10871635887a(28) =22548578220a(29) =46707769257