Index of 9^n within the sequence of the numbers of the form 8^i*9^j.

Terms

a(0) =1a(1) =3a(2) =6a(3) =10a(4) =15a(5) =21a(6) =28a(7) =36a(8) =45a(9) =55a(10) =66a(11) =78a(12) =91a(13) =105a(14) =120a(15) =136a(16) =153a(17) =171a(18) =191a(19) =212a(20) =234a(21) =257a(22) =281a(23) =306a(24) =332a(25) =359a(26) =387a(27) =416a(28) =446a(29) =477