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A090264
Numbers n such that the strings n7n and 7n7 are both prime.
4
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
EXAMPLE
131 is a member as 1317131 and 71317 are both prime.
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Nov 28 2003
EXTENSIONS
More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004
STATUS
approved