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%I #9 Dec 05 2013 19:55:12
%S 3,7,17,31,49,57,111,169,269,363,389,393,637,643,671,697,787,851,853,
%T 927,1033,1087,1089,1151,1153,1173,1217,1219,1233,1261,1331,1479,1671,
%U 1761,1767,1837,1841,1859,1921,2011,2147,2149,2283,2311,2353,2377,2409
%N Numbers n such that the concatenations n, n-2, n and n, n+2, n are primes.
%e 17 belongs to this sequence for 171517 as well as 171917 are primes.
%t 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 *)
%Y Cf. A068680, A068681.
%K base,hard,nonn
%O 1,1
%A _Amarnath Murthy_, Mar 02 2002
%E More terms from _Sascha Kurz_, Mar 26 2002
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