Index of 10^n within the sequence of the numbers of the form 6^i*10^j.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =16a(5) =23a(6) =31a(7) =40a(8) =51a(9) =63a(10) =76a(11) =91a(12) =107a(13) =124a(14) =142a(15) =162a(16) =183a(17) =205a(18) =229a(19) =254a(20) =280a(21) =307a(22) =336a(23) =366a(24) =397a(25) =430a(26) =464a(27) =499a(28) =535a(29) =573