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