a(n) = round(3^n/5).

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =16a(5) =49a(6) =146a(7) =437a(8) =1312a(9) =3937a(10) =11810a(11) =35429a(12) =106288a(13) =318865a(14) =956594a(15) =2869781a(16) =8609344a(17) =25828033a(18) =77484098a(19) =232452293a(20) =697356880a(21) =2092070641a(22) =6276211922a(23) =18828635765a(24) =56485907296a(25) =169457721889a(26) =508373165666