a(n) = floor(3^n/(3n-1)).

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =17a(5) =42a(6) =109a(7) =285a(8) =757a(9) =2036a(10) =5535a(11) =15184a(12) =41955a(13) =116657a(14) =326111a(15) =915887a(16) =2582803a(17) =7309820a(18) =20754669a(19) =59098040a(20) =168715374a(21) =482785532a(22) =1384458512a(23) =3977880795a(24) =11449846073a(25) =33011244523a(26) =95319968562a(27) =275624005481a(28) =798027643777