Numbers of form 4^i*10^j, with i, j >= 0.

Terms

a(0) =1a(1) =4a(2) =10a(3) =16a(4) =40a(5) =64a(6) =100a(7) =160a(8) =256a(9) =400a(10) =640a(11) =1000a(12) =1024a(13) =1600a(14) =2560a(15) =4000a(16) =4096a(17) =6400a(18) =10000a(19) =10240a(20) =16000a(21) =16384a(22) =25600a(23) =40000a(24) =40960a(25) =64000a(26) =65536a(27) =100000a(28) =102400a(29) =160000