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A046035
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Numbers k such that the concatenation of the first k primes (A019518) is a prime.
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14
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OFFSET
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1,2
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COMMENTS
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REFERENCES
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R. Crandall and C. Pomerance, Prime Numbers: A Computational Perspective, Springer, NY, 2001; see p. 72. [The 2002 printing states incorrectly that 719 is a term.]
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LINKS
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FORMULA
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EXAMPLE
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4 is a term since 2357 is a prime. [Corrected by Ed Murphy (emurphy42(AT)socal.rr.com), May 15 2007]
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MATHEMATICA
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max = 1500; With[{primes = Prime[Range[max]]}, Flatten[Position[ Table[ FromDigits[Flatten[IntegerDigits/@Take[primes, n]]], {n, max}], _?PrimeQ]]] (* Harvey P. Dale, Dec 17 2013 *)
Position[FromDigits /@ Rest[FoldList[Join, {}, IntegerDigits[Prime[Range[ 10^3]]]]], _?PrimeQ] // Flatten (* Eric W. Weisstein, Oct 30 2015 *)
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PROG
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(PARI) p=""; for(n=1, 2000, p=concat(p, prime(n)); if(ispseudoprime(eval(p)), print1(n", "))) \\ Altug Alkan, Oct 30 2015
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CROSSREFS
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Cf. A033308 (Decimal expansion of Copeland-Erdős constant: concatenate primes).
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KEYWORD
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nonn,base,nice
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AUTHOR
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STATUS
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approved
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