a(n) = 11 + floor( (1 + Sum_{j=1..n-1} a(j)) / 2).

Terms

a(0) =11a(1) =17a(2) =25a(3) =38a(4) =57a(5) =85a(6) =128a(7) =192a(8) =288a(9) =432a(10) =648a(11) =972a(12) =1458a(13) =2187a(14) =3280a(15) =4920a(16) =7380a(17) =11070a(18) =16605a(19) =24908a(20) =37362a(21) =56043a(22) =84064a(23) =126096a(24) =189144a(25) =283716a(26) =425574a(27) =638361a(28) =957542a(29) =1436313