a(1) = 3; for n>0, a(n+1) = a(n) + floor((a(n)-1)/2).

Terms

a(0) =3a(1) =4a(2) =5a(3) =7a(4) =10a(5) =14a(6) =20a(7) =29a(8) =43a(9) =64a(10) =95a(11) =142a(12) =212a(13) =317a(14) =475a(15) =712a(16) =1067a(17) =1600a(18) =2399a(19) =3598a(20) =5396a(21) =8093a(22) =12139a(23) =18208a(24) =27311a(25) =40966a(26) =61448a(27) =92171a(28) =138256a(29) =207383