A102502 Values of n for which the concatenation 9nn9 (from sequence A102484) are primes.

10, 13, 16, 17, 20, 23, 28, 31, 35, 37, 46, 53, 56, 61, 65, 68, 74, 82, 94, 95, 98, 1010, 1013, 1018, 1042, 1048, 1051, 1052, 1063, 1072, 1073, 1082, 1103, 1114, 1124, 1129, 1139, 1142, 1171, 1192, 1193, 1195, 1208, 1214, 1240, 1241, 1244, 1249, 1258, 1271

Offset: 1

Author

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

Keywords

• easy
• nonn
• base

Examples

			The number 910109 is prime and corresponds to n=10.
The number 9101310139 is prime and corresponds to n=1013.
		

Crossrefs

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

Programs

Mathematica

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

Extensions

More terms from Robert G. Wilson v, Jan 14 2005