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Search: id:A152014
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| A152014 |
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Number of n-digit primes whose reversal is a different prime. |
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+0
3
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OFFSET
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1,2
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COMMENT
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All terms are even.
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EXAMPLE
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a(1)=0 because there are no 1-digit terms in A006567, a(2)=8 because there are eight 2-digit terms in A006567: 13,17,31,37,71,73,79,97.
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MATHEMATICA
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Do[c = 0; p = NextPrime[10^(n - 1) - 1]; n1 = PrimePi[p]; n2 = PrimePi[NextPrime[10^n, -1]] - n1 + 1; Do[id = IntegerDigits[p]; i1 = id[[1]]; If[OddQ[i1] && i1 != 5, p1 = FromDigits[ Reverse[id]]; If[p1 != p, If[PrimeQ[p1], c++ ]]]; p = NextPrime[p], {n2}]; Print[{n, c}], {n, 1, 9}];
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CROSSREFS
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Cf. A006567 Emirps (primes whose reversal is a different prime).
Sequence in context: A110046 A027380 A058289 this_sequence A146977 A068623 A155578
Adjacent sequences: A152011 A152012 A152013 this_sequence A152015 A152016 A152017
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KEYWORD
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more,nonn,base
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AUTHOR
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Zak Seidov (zakseidov(AT)yahoo.com), Nov 19 2008
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