Index of 7^n within the sequence of the numbers of the form 7^i*8^j.

Terms

a(0) =1a(1) =2a(2) =4a(3) =7a(4) =11a(5) =16a(6) =22a(7) =29a(8) =37a(9) =46a(10) =56a(11) =67a(12) =79a(13) =92a(14) =106a(15) =121a(16) =136a(17) =152a(18) =169a(19) =187a(20) =206a(21) =226a(22) =247a(23) =269a(24) =292a(25) =316a(26) =341a(27) =367a(28) =394a(29) =422