Numbers of the form 2^i*5^j where i+j is even.

Terms

a(0) =1a(1) =4a(2) =10a(3) =16a(4) =25a(5) =40a(6) =64a(7) =100a(8) =160a(9) =250a(10) =256a(11) =400a(12) =625a(13) =640a(14) =1000a(15) =1024a(16) =1600a(17) =2500a(18) =2560a(19) =4000a(20) =4096a(21) =6250a(22) =6400a(23) =10000a(24) =10240a(25) =15625a(26) =16000a(27) =16384a(28) =25000a(29) =25600