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Search: id:A091638
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| A091638 |
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Number of primes less than 10^n which do not contain the digit 4. |
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+0
11
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| 4, 22, 136, 903, 6361, 46545, 354123, 2761106, 21925170, 176544507, 1437663500, 11814853749
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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Number of primes less than 10^n after removing any primes with at least one digit 4.
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EXAMPLE
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a(2) = 22 because of the 25 primes less than 10^2, 3 have at least one digit 4; 25-3 = 22.
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MATHEMATICA
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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}] (from Robert G. Wilson v Feb 02 2004)
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CROSSREFS
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a(n) + A091705(n) = A006880(n).
Cf. A091634, A091635, A091636, A091637, A091639, A091640, A091641, A091642, A091643.
Sequence in context: A143648 A069835 A007196 this_sequence A142984 A097593 A025756
Adjacent sequences: A091635 A091636 A091637 this_sequence A091639 A091640 A091641
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KEYWORD
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more,nonn,base
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AUTHOR
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Enoch Haga (Enokh(AT)comcast.net), Jan 30 2004
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EXTENSIONS
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Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 02 2004
a(9)-a(12) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Feb 14 2008
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