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Search: id:A091641
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| A091641 |
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Number of primes less than 10^n which do not contain the digit 7. |
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+0
11
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| 3, 16, 100, 680, 4773, 34992, 266823, 2079512, 16503238, 132852644, 1081509855, 8885472675
(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 7.
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EXAMPLE
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a(2) = 16 because of the 25 primes less than 10^2, 9 have at least one digit 7; 25-9=16.
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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], 7] == {}, 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) + A091708(n) = A006880(n).
Cf. A091634, A091635, A091636, A091637, A091638, A091639, A091640, A091642, A091643.
Sequence in context: A000270 A000271 A074553 this_sequence A137572 A009151 A009007
Adjacent sequences: A091638 A091639 A091640 this_sequence A091642 A091643 A091644
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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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