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 A091643 Number of primes less than 10^n which do not contain the digit 9. 30
 4, 19, 108, 687, 4766, 35139, 267486, 2083814, 16531372, 133059504, 1082995490, 8896945667, 73651718719, 613664827254 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA Number of primes less than 10^n after removing any primes with at least one digit 9. a(n) = A006880(n) - A091710(n). a(n) <= max(4,24*(9^(n-2))) <= 1 + (9^n)/3 (see formula in A091634). - Chai Wah Wu, Sep 17 2018 EXAMPLE a(2) = 19 because of the 25 primes less than 10^2, 6 have at least one digit 9; 25-6 = 19. MATHEMATICA 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 *) CROSSREFS Cf. A091634, A091635, A091636, A091637, A091638, A091639, A091640, A091641, A091642. Sequence in context: A241839 A218183 A206227 * A323620 A306183 A241840 Adjacent sequences:  A091640 A091641 A091642 * A091644 A091645 A091646 KEYWORD more,nonn,base AUTHOR Enoch Haga, Jan 30 2004 EXTENSIONS Edited and extended by Robert G. Wilson v, Feb 02 2004 a(9)-a(12) from Donovan Johnson, Feb 14 2008 a(13) from Robert Price, Nov 08 2013 a(14) from Giovanni Resta, Mar 20 2017 STATUS approved

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Last modified March 29 20:20 EDT 2020. Contains 333117 sequences. (Running on oeis4.)