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 A091638 #13 Mar 20 2017 04:39:11
%S A091638 4,22,136,903,6361,46545,354123,2761106,21925170,176544507,1437663500,
%T A091638 11814853749,97837428598,815398741896
%N A091638 Number of primes less than 10^n which do not contain the digit 4.
%F A091638 Number of primes less than 10^n after removing any primes with at least one digit 4.
%F A091638 a(n) = A006880(n) - A091705(n).
%e A091638 a(2) = 22 because of the 25 primes less than 10^2, 3 have at least one digit 4; 25-3 = 22.
%t A091638 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], 4] == {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* _Robert G. Wilson v_, Feb 02 2004 *)
%Y A091638 Cf. A091634, A091635, A091636, A091637, A091639, A091640, A091641, A091642, A091643.
%K A091638 more,nonn,base
%O A091638 1,1
%A A091638 _Enoch Haga_, Jan 30 2004
%E A091638 Edited and extended by _Robert G. Wilson v_, Feb 02 2004
%E A091638 a(9)-a(12) from _Donovan Johnson_, Feb 14 2008
%E A091638 a(13) from _Robert Price_, Nov 08 2013
%E A091638 a(14) from _Giovanni Resta_, Mar 20 2017