A068682 Numbers n such that the concatenations n, n-2, n and n, n+2, n are primes.

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

Offset

1,1

Links

Table of n, a(n) for n=1..47.

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 A364189

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