A069688 Primes that yield another prime on placing a 3 on both sides (as leading and trailing digits).

5, 7, 31, 37, 41, 43, 53, 59, 61, 67, 73, 79, 83, 101, 103, 139, 151, 157, 179, 197, 223, 241, 257, 263, 269, 271, 283, 293, 307, 311, 349, 353, 389, 421, 431, 461, 467, 491, 557, 593, 599, 601, 607, 631, 643, 647, 683, 691, 701, 727, 757, 769, 811, 827, 839

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..10000

Example

139 is a member as 31393 is also a prime.

Mathematica

Select[ Range[1000], PrimeQ[ # ] && PrimeQ[ FromDigits[ Insert[ IntegerDigits[ # ], 3, {{1}, {-1}}]]] &]
Select[Prime[Range[200]], PrimeQ[FromDigits[Join[{3}, IntegerDigits[#], {3}]]]&] (* Harvey P. Dale, Oct 24 2011 *)

Crossrefs

Cf. A069687, A069689, A069690.

Sequence in context: A307532 A135324 A107639 * A158323 A025119 A025095

Adjacent sequences: A069685 A069686 A069687 * A069689 A069690 A069691

Keyword

nonn,base

Author

Amarnath Murthy, Apr 06 2002

Extensions

Edited and extended by Robert G. Wilson v, May 03 2002

Status

approved