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 A091640 #17 Apr 23 2021 11:55:51
%S A091640 4,23,136,897,6367,46706,355148,2770239,21984207,176966593,1440765209,
%T A091640 11838096715,98014747908,816769206831
%N A091640 Number of primes less than 10^n which do not contain the digit 6.
%F A091640 Number of primes less than 10^n after removing any primes with at least one digit 6.
%F A091640 a(n) = A006880(n) - A091707(n).
%e A091640 a(2) = 23 because of the 25 primes less than 10^2, 2 have at least one digit 6; 25-2 = 23.
%t A091640 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], 6] == {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* _Robert G. Wilson v_, Feb 02 2004 *)
%o A091640 (Python)
%o A091640 from sympy import sieve # use slower primerange for larger terms
%o A091640 def a(n): return sum('6' not in str(p) for p in sieve.primerange(2, 10**n))
%o A091640 print([a(n) for n in range(1, 8)]) # _Michael S. Branicky_, Apr 23 2021
%Y A091640 Cf. A091634, A091635, A091636, A091637, A091638, A091639, A091641, A091642, A091643.
%K A091640 more,nonn,base
%O A091640 1,1
%A A091640 _Enoch Haga_, Jan 30 2004
%E A091640 Edited and extended by _Robert G. Wilson v_, Feb 02 2004
%E A091640 a(9)-a(12) from _Donovan Johnson_, Feb 14 2008
%E A091640 a(13) from _Robert Price_, Nov 08 2013
%E A091640 a(14) from _Giovanni Resta_, Mar 20 2017