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A166283
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Primes such that the concatenation of its index and itself is a prime.
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2
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3, 7, 13, 37, 59, 61, 83, 103, 113, 149, 151, 179, 181, 197, 199, 251, 263, 269, 271, 283, 353, 421, 431, 439, 479, 487, 523, 631, 643, 653, 661, 677, 709, 769, 811, 829, 853, 937, 947, 1019, 1039, 1049, 1051, 1277, 1319, 1399, 1427, 1433, 1489, 1543, 1663
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OFFSET
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1,1
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LINKS
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EXAMPLE
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The prime, 3 has an index of 2, i.e.; pi(3) = 2 and the concatenation, 23 is a prime.
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MATHEMATICA
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Select[ Prime@ Range@ 273, PrimeQ@ FromDigits@ Join[ IntegerDigits@ PrimePi@#, IntegerDigits@# ] &]
Select[Table[{n, Prime[n]}, {n, 300}], PrimeQ[#[[1]]*10^IntegerLength[ #[[2]]]+ #[[2]]]&][[All, 2]] (* Harvey P. Dale, Jun 01 2017 *)
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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