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

Terms

a(0) =0a(1) =24a(2) =192a(3) =1248a(4) =7680a(5) =46464a(6) =279552a(7) =1678848a(8) =10076160a(9) =60463104a(10) =362790912a(11) =2176770048a(12) =13060669440a(13) =78364114944a(14) =470184886272