Index of 5^n within the sequence of the numbers of the form 5^i*10^j.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =10a(5) =14a(6) =19a(7) =24a(8) =30a(9) =37a(10) =44a(11) =52a(12) =61a(13) =71a(14) =81a(15) =92a(16) =104a(17) =116a(18) =129a(19) =143a(20) =157a(21) =172a(22) =188a(23) =205a(24) =222a(25) =240a(26) =259a(27) =278a(28) =298a(29) =319