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

Terms

a(0) =0a(1) =1a(2) =10a(3) =57a(4) =260a(5) =1055a(6) =3990a(7) =14413a(8) =50440a(9) =172539a(10) =580250a(11) =1926089a(12) =6328140a(13) =20619703a(14) =66732190a(15) =214742085a(16) =687698960a(17) =2193154547a(18) =6968850210a(19) =22073006401a(20) =69714716500a(21) =219623377071a(22) =690291036710