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A261493
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Palindromes that are concatenation of palindromic prime numbers in increasing order up to the n-th and then in decreasing order.
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1
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2, 232, 23532, 2357532, 2357117532, 235711101117532, 235711101131101117532, 235711101131151131101117532, 235711101131151181151131101117532, 235711101131151181191181151131101117532, 235711101131151181191313191181151131101117532
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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For n=6, the first 6 palindromic primes are 2,3,5,7,11,101. Relevant subsequence that produce a(6) is 2,3,5,7,11,101,11,7,5,3,2. Concatenation of items with that order determines a(6) = 235711101117532.
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MATHEMATICA
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palQ[n_] := Reverse[idn = IntegerDigits@ n] == idn; s = Select[ Prime@ Range@ 1000, palQ]; f[n_] := FromDigits@ Flatten[ IntegerDigits@# & /@ Join[ Take[s, n], Reverse@ Take[s, n - 1]]]; Array[f, 11] (* Robert G. Wilson v, Aug 24 2015 *)
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CROSSREFS
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KEYWORD
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nonn,easy,base
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AUTHOR
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STATUS
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approved
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