Index of 2^n within sequence of numbers of form 2^i * 5^j.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =7a(5) =10a(6) =13a(7) =17a(8) =21a(9) =25a(10) =30a(11) =35a(12) =41a(13) =47a(14) =54a(15) =61a(16) =68a(17) =76a(18) =84a(19) =93a(20) =102a(21) =112a(22) =122a(23) =132a(24) =143a(25) =154a(26) =166a(27) =178a(28) =191a(29) =204