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 A091639 Number of primes less than 10^n which do not contain the digit 5. 10
 3, 22, 136, 905, 6310, 46549, 354910, 2765749, 21955845, 176781643, 1439380189, 11827571824, 97933795005, 816144146010 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Number of primes less than 10^n after removing any primes with at least one digit 5. LINKS FORMULA a(n) = A006880(n) - A091706(n). EXAMPLE a(2) = 22 because of the 25 primes less than 10^2, 3 have at least one digit 5; 25-3 = 22. 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], 5] == {}, c++ ]]; Print[c]; p--, {n, 1, 8}] (* Robert G. Wilson v, Feb 02 2004 *) PROG (Python) from sympy import primerange def a(n): return sum('5' not in str(p) for p in primerange(2, 10**n)) print([a(n) for n in range(1, 7)]) # Michael S. Branicky, Mar 22 2021 CROSSREFS Cf. A091634, A091635, A091636, A091637, A091638, A091640, A091641, A091642, A091643. Cf. A006880, A091706. Sequence in context: A232017 A100511 A033506 * A091636 A321003 A339227 Adjacent sequences:  A091636 A091637 A091638 * A091640 A091641 A091642 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 May 5 19:09 EDT 2021. Contains 343573 sequences. (Running on oeis4.)