A102502 - OEIS

%I #7 Mar 14 2015 16:59:21

%S 10,13,16,17,20,23,28,31,35,37,46,53,56,61,65,68,74,82,94,95,98,1010,

%T 1013,1018,1042,1048,1051,1052,1063,1072,1073,1082,1103,1114,1124,

%U 1129,1139,1142,1171,1192,1193,1195,1208,1214,1240,1241,1244,1249,1258,1271

%N Values of n for which the concatenation 9nn9 (from sequence A102484) are primes.

%e The number 910109 is prime and corresponds to n=10.

%e The number 9101310139 is prime and corresponds to n=1013.

%t fQ[n_] := Block[{id = IntegerDigits[n]}, PrimeQ[ FromDigits[ Join[{9}, id, id, {9}]]]]; Select[ Range[1288], fQ[ # ] &] (* _Robert G. Wilson v_, Jan 14 2004 *)

%Y The full sequence of integers of the form 9nn9 is A102484. The primes that correspond to these values of n are sequence A102503.

%K easy,nonn,base

%O 1,1

%A Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 13 2005

%E More terms from _Robert G. Wilson v_, Jan 14 2005