a(n+1) = a(n)+floor(a(n)/3), a(1) = 3.

Terms

a(0) =3a(1) =4a(2) =5a(3) =6a(4) =8a(5) =10a(6) =13a(7) =17a(8) =22a(9) =29a(10) =38a(11) =50a(12) =66a(13) =88a(14) =117a(15) =156a(16) =208a(17) =277a(18) =369a(19) =492a(20) =656a(21) =874a(22) =1165a(23) =1553a(24) =2070a(25) =2760a(26) =3680a(27) =4906a(28) =6541a(29) =8721