Lower (1/5,1/2) midsequence of (2^n) and (5*n); see Comments.

Terms

a(0) =0a(1) =2a(2) =5a(3) =9a(4) =13a(5) =18a(6) =27a(7) =43a(8) =71a(9) =124a(10) =229a(11) =437a(12) =849a(13) =1670a(14) =3311a(15) =6591a(16) =13147a(17) =26256a(18) =52473a(19) =104905a(20) =209765a(21) =419482a(22) =838915a(23) =1677779a(24) =3355503a(25) =6710948a(26) =13421837a(27) =26843613a(28) =53687161a(29) =107374254