a(n) = 14 + floor((1 + Sum_{j=1..n-1} a(j))/3).

Terms

a(0) =14a(1) =19a(2) =25a(3) =33a(4) =44a(5) =59a(6) =79a(7) =105a(8) =140a(9) =187a(10) =249a(11) =332a(12) =443a(13) =590a(14) =787a(15) =1049a(16) =1399a(17) =1865a(18) =2487a(19) =3316a(20) =4421a(21) =5895a(22) =7860a(23) =10480a(24) =13973a(25) =18631a(26) =24841a(27) =33122a(28) =44162a(29) =58883