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Search: id:A114018
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| A114018 |
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Least n-digit prime whose digit reversal is also prime. |
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+0
7
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| 2, 11, 101, 1009, 10007, 100049, 1000033, 10000169, 100000007, 1000000007, 10000000207, 100000000237, 1000000000091, 10000000000313, 100000000000261, 1000000000000273, 10000000000000079, 100000000000000049
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The more compact version A168159 gives many more terms, cf. formula. [From M. F. Hasler (mhasler(AT)univ-ag.fr), Nov 21 2009]
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FORMULA
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a(n)=10^(n-1)+A168159(n) [From M. F. Hasler (mhasler(AT)univ-ag.fr), Nov 21 2009]
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MATHEMATICA
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f[n_] := Block[{k = 10^(n - 1)}, While[ !PrimeQ[k] || !PrimeQ[FromDigits@Reverse@IntegerDigits@k], k++ ]; k]; Array[f, 19] (* Robert G. Wilson v *)
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PROGRAM
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(PARI) for(x=1, 1e99, until( isprime(x=nextprime(x+1)) & isprime(eval(concat(vecextract(Vec(Str(x)), "-1..1")))), ); print1(x", "); x=10^#Str(x)-1) \\ [From M. F. Hasler (mhasler(AT)univ-ag.fr), Nov 21 2009]
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CROSSREFS
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Sequence in context: A062397 A158578 A003617 this_sequence A089770 A069663 A121419
Cf. A168159, A007500, A006567, A122490. [From M. F. Hasler (mhasler(AT)univ-ag.fr), Nov 21 2009]
Adjacent sequences: A114015 A114016 A114017 this_sequence A114019 A114020 A114021
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KEYWORD
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base,nonn,new
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 12 2005
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(at)rgwv.com), Nov 19 2005
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