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 A046035 Numbers n such that the concatenation of the first n primes (A019518) is a prime. 14
 1, 2, 4, 128, 174, 342, 435, 1429 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS No others with n <= 34736. - Eric W. Weisstein, Oct 30 2015 REFERENCES 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.] LINKS M. Fleuren, Smarandache Concatenated Primes. Eric Weisstein's World of Mathematics, Consecutive Number Sequences Eric Weisstein's World of Mathematics, Integer Sequence Primes Eric Weisstein's World of Mathematics, Smaradache-Wellin Prime FORMULA a(n) = A000720(A046284(n)), or A046284(n) = prime(a(n)). EXAMPLE 4 is a term since 2357 is a prime. [Corrected by Ed Murphy (emurphy42(AT)socal.rr.com), May 15 2007] MATHEMATICA 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 *) PROG (PARI) p=""; for(n=1, 2000, p=concat(p, prime(n)); if(ispseudoprime(eval(p)), print1(n", "))) \\ Altug Alkan, Oct 30 2015 CROSSREFS Cf. A019518, A069151, A046284. Cf. A033308 (Decimal expansion of Copeland-Erdős constant: concatenate primes). Sequence in context: A259381 A009595 A018493 * A134710 A009073 A326213 Adjacent sequences:  A046032 A046033 A046034 * A046036 A046037 A046038 KEYWORD nonn,base,nice AUTHOR STATUS approved

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Last modified October 19 15:50 EDT 2019. Contains 328223 sequences. (Running on oeis4.)