a(n+1) = a(n) + floor(a(n)/4) with a(0)=4.

Terms

a(0) =4a(1) =5a(2) =6a(3) =7a(4) =8a(5) =10a(6) =12a(7) =15a(8) =18a(9) =22a(10) =27a(11) =33a(12) =41a(13) =51a(14) =63a(15) =78a(16) =97a(17) =121a(18) =151a(19) =188a(20) =235a(21) =293a(22) =366a(23) =457a(24) =571a(25) =713a(26) =891a(27) =1113a(28) =1391a(29) =1738