a(n) = 7 + floor((2 + Sum_{j=1..n-1} a(j))/3).

Terms

a(0) =7a(1) =10a(2) =13a(3) =17a(4) =23a(5) =31a(6) =41a(7) =55a(8) =73a(9) =97a(10) =130a(11) =173a(12) =231a(13) =308a(14) =410a(15) =547a(16) =729a(17) =972a(18) =1296a(19) =1728a(20) =2304a(21) =3072a(22) =4096a(23) =5462a(24) =7282a(25) =9710a(26) =12946a(27) =17262a(28) =23016a(29) =30688