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 A068682 Numbers n such that the concatenations n, n-2, n and n, n+2, n are primes. 0
 3, 7, 17, 31, 49, 57, 111, 169, 269, 363, 389, 393, 637, 643, 671, 697, 787, 851, 853, 927, 1033, 1087, 1089, 1151, 1153, 1173, 1217, 1219, 1233, 1261, 1331, 1479, 1671, 1761, 1767, 1837, 1841, 1859, 1921, 2011, 2147, 2149, 2283, 2311, 2353, 2377, 2409 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE 17 belongs to this sequence for 171517 as well as 171917 are primes. MATHEMATICA d[n_] := IntegerDigits[n]; Select[Range[2410], And@@PrimeQ[FromDigits/@{Join[d[#], d[#-2], d[#]], Join[d[#], d[#+2], d[#]]}] &] (* Jayanta Basu, May 20 2013 *) CROSSREFS Cf. A068680, A068681. Sequence in context: A228567 A123988 A006628 * A292446 A045425 A099983 Adjacent sequences:  A068679 A068680 A068681 * A068683 A068684 A068685 KEYWORD base,hard,nonn AUTHOR Amarnath Murthy, Mar 02 2002 EXTENSIONS More terms from Sascha Kurz, Mar 26 2002 STATUS approved

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Last modified January 22 19:39 EST 2020. Contains 331153 sequences. (Running on oeis4.)