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 A244085 Primes p such that the concatenation of p and 2*p-1 is also prime. 1
 2, 5, 17, 29, 47, 61, 137, 149, 179, 181, 227, 251, 349, 367, 409, 457, 461, 479, 487, 557, 569, 617, 661, 691, 761, 787, 809, 821, 859, 911, 971, 977, 997, 1039, 1117, 1129, 1151, 1249, 1277, 1367, 1439, 1447, 1459, 1481, 1559, 1571, 1667, 1747, 1801, 1831 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The corresponding prime numbers are: (23, 59, 1733, 2957, 4793, 61121, ...). LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 EXAMPLE 17 in this sequence because the concatenation of 17 and 33 is 1733 prime. MATHEMATICA p2pQ[n_]:=PrimeQ[FromDigits[IntegerDigits/@Join[n, 2 n - 1]]]; Select[Prime[Range[900]], p2pQ] CROSSREFS Cf. A168164. Sequence in context: A195271 A077217 A120847 * A019353 A106882 A172122 Adjacent sequences: A244082 A244083 A244084 * A244086 A244087 A244088 KEYWORD nonn,base AUTHOR Vincenzo Librandi, Jun 22 2014 STATUS approved

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Last modified February 27 14:08 EST 2024. Contains 370375 sequences. (Running on oeis4.)