a(n) = floor(3^n / n).

Terms

a(0) =3a(1) =4a(2) =9a(3) =20a(4) =48a(5) =121a(6) =312a(7) =820a(8) =2187a(9) =5904a(10) =16104a(11) =44286a(12) =122640a(13) =341640a(14) =956593a(15) =2690420a(16) =7596480a(17) =21523360a(18) =61171656a(19) =174339220a(20) =498112057a(21) =1426411800a(22) =4093181688a(23) =11767897353a(24) =33891544377a(25) =97764070320a(26) =282429536481