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 A103965 Numbers n such that the string n10n is the decimal expansion of a prime number. 0
 9, 27, 41, 81, 111, 113, 117, 183, 191, 219, 231, 261, 279, 281, 309, 321, 339, 363, 377, 399, 401, 411, 429, 449, 461, 467, 477, 479, 497, 503, 513, 539, 549, 567, 603, 633, 653, 659, 689, 693, 707, 723, 731, 737, 747, 773, 843, 849, 887, 891, 911, 917 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE n=9 is in the sequence because n10n = 9109 is prime. n=113 is in the sequence because n10n = 11310113 is prime. n=219 is in the sequence because n10n = 21910219 is prime. MATHEMATICA n10pQ[n_]:=Module[{idn=IntegerDigits[n]}, PrimeQ[FromDigits[Join[idn, {1, 0}, idn]]]] Select[Range[1000], n10pQ]  (* Harvey P. Dale, Feb 22 2011 *) PROG (MAGMA) [ n: n in [0..1000] | IsPrime(Seqint(Intseq(n) cat [0, 1] cat Intseq(n))) ]; // Klaus Brockhaus, Feb 03 2011 CROSSREFS Sequence in context: A116455 A103753 A238333 * A069069 A031088 A020156 Adjacent sequences:  A103962 A103963 A103964 * A103966 A103967 A103968 KEYWORD base,nonn AUTHOR Parthasarathy Nambi, Mar 30 2005 STATUS approved

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Last modified February 16 21:46 EST 2020. Contains 331975 sequences. (Running on oeis4.)