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Search: id:A057708
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| A057708 |
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Numbers n such that 2^n reversed is prime. |
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+0
8
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| 1, 4, 5, 7, 10, 17, 24, 37, 45, 55, 70, 77, 107, 137, 150, 271, 364, 1157, 1656, 2004, 2126, 3033, 3489, 3645, 4336, 6597, 7279, 12690, 13840, 20108, 21693, 28888
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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4 is a member because 2^4 reversed is 61 and prime.
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MAPLE
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with(numtheory): myarray := []: for n from 1 to 4000 do it1 := convert(2^n, base, 10): it2 := sum(10^(nops(it1)-i)*it1[i], i=1..nops(it1)): if isprime(it2) then printf(`%d, `, n) fi: od:
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MATHEMATICA
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Do[ If[ PrimeQ[ FromDigits[ Reverse[ IntegerDigits[2^n]] ]], Print[ n]], {n, 20000}] (from Robert G. Wilson v Jan 29 2005)
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CROSSREFS
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Sequence in context: A018910 A022936 A057496 this_sequence A032686 A074300 A047375
Adjacent sequences: A057705 A057706 A057707 this_sequence A057709 A057710 A057711
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KEYWORD
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base,nonn
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AUTHOR
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G. L. Honaker, Jr. (honak3r(AT)bvunet.net), Oct 23 2000
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EXTENSIONS
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More terms from Chris Nash (chris_nash(AT)prodigy.net), Oct 25 2000. Two more terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 29 2001.
3 more terms from Farideh Firoozbakht (f.firoozbakht(AT)math.ui.ac.ir), Aug 05 2004
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