Index of 5^n within the sequence of the numbers of the form 5^i*9^j.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =10a(5) =14a(6) =19a(7) =25a(8) =31a(9) =38a(10) =46a(11) =55a(12) =64a(13) =74a(14) =85a(15) =96a(16) =108a(17) =121a(18) =135a(19) =149a(20) =164a(21) =180a(22) =197a(23) =214a(24) =232a(25) =251a(26) =271a(27) =291a(28) =312a(29) =334