a(n)=2*a(n-1), except every tenth time you multiply by 1000/512 instead of by 2.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =16a(5) =32a(6) =64a(7) =128a(8) =256a(9) =512a(10) =1000a(11) =2000a(12) =4000a(13) =8000a(14) =16000a(15) =32000a(16) =64000a(17) =128000a(18) =256000a(19) =512000a(20) =1000000a(21) =2000000a(22) =4000000a(23) =8000000a(24) =16000000a(25) =32000000a(26) =64000000a(27) =128000000a(28) =256000000a(29) =512000000