Index of 10^n within the sequence of the numbers of the form 4^i*10^j.

Terms

a(0) =1a(1) =3a(2) =7a(3) =12a(4) =19a(5) =28a(6) =38a(7) =50a(8) =64a(9) =79a(10) =96a(11) =115a(12) =135a(13) =157a(14) =181a(15) =206a(16) =233a(17) =262a(18) =292a(19) =324a(20) =358a(21) =393a(22) =430a(23) =469a(24) =509a(25) =551a(26) =595a(27) =640a(28) =687a(29) =736