Index of 10^n within the sequence of the numbers of the form 9^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) =66a(11) =78a(12) =91a(13) =105a(14) =120a(15) =136a(16) =153a(17) =171a(18) =190a(19) =210a(20) =231a(21) =254a(22) =278a(23) =303a(24) =329a(25) =356a(26) =384a(27) =413a(28) =443a(29) =474