A090264 Numbers n such that the strings n7n and 7n7 are both prime.

131, 153, 191, 233, 261, 327, 341, 359, 389, 407, 429, 459, 489, 527, 533, 579, 593, 599, 671, 683, 701, 723, 731, 797, 813, 869, 873, 939, 981, 1083, 1097, 1109, 1143, 1187, 1241, 1283, 1317, 1391, 1437, 1451, 1539, 1553, 1871, 1889, 1893, 2049, 2111

Offset

1,1

Links

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Example

131 is a member as 1317131 and 71317 are both prime.

Crossrefs

Cf. A090262, A090263, A090265.

Sequence in context: A164294 A155924 A270237 * A345520 A345774 A132254

Adjacent sequences: A090261 A090262 A090263 * A090265 A090266 A090267

Keyword

base,nonn

Author

Amarnath Murthy, Nov 28 2003

Extensions

More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004

Status

approved