Index of 10^n within the sequence of the numbers of the form 8^i*10^j.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =15a(5) =21a(6) =28a(7) =36a(8) =45a(9) =55a(10) =67a(11) =80a(12) =94a(13) =109a(14) =125a(15) =142a(16) =160a(17) =179a(18) =199a(19) =221a(20) =244a(21) =268a(22) =293a(23) =319a(24) =346a(25) =374a(26) =403a(27) =433a(28) =465a(29) =498