This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A091643 #20 Sep 17 2018 20:39:47
%S A091643 4,19,108,687,4766,35139,267486,2083814,16531372,133059504,1082995490,
%T A091643 8896945667,73651718719,613664827254
%N A091643 Number of primes less than 10^n which do not contain the digit 9.
%F A091643 Number of primes less than 10^n after removing any primes with at least one digit 9.
%F A091643 a(n) = A006880(n) - A091710(n).
%F A091643 a(n) <= max(4,24*(9^(n-2))) <= 1 + (9^n)/3 (see formula in A091634). - _Chai Wah Wu_, Sep 17 2018
%e A091643 a(2) = 19 because of the 25 primes less than 10^2, 6 have at least one digit 9; 25-6 = 19.
%t A091643 NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; c = 0; p = 1; Do[ While[ p = NextPrim[p]; p < 10^n, If[ Position[ IntegerDigits[p], 9] == {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* _Robert G. Wilson v_, Feb 02 2004 *)
%Y A091643 Cf. A091634, A091635, A091636, A091637, A091638, A091639, A091640, A091641, A091642.
%K A091643 more,nonn,base
%O A091643 1,1
%A A091643 _Enoch Haga_, Jan 30 2004
%E A091643 Edited and extended by _Robert G. Wilson v_, Feb 02 2004
%E A091643 a(9)-a(12) from _Donovan Johnson_, Feb 14 2008
%E A091643 a(13) from _Robert Price_, Nov 08 2013
%E A091643 a(14) from _Giovanni Resta_, Mar 20 2017