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A090263
Numbers n such that the strings n3n and 3n3 are both prime.
5
1, 37, 41, 53, 59, 79, 83, 119, 133, 151, 179, 197, 223, 241, 263, 283, 299, 349, 361, 377, 427, 461, 553, 559, 593, 599, 637, 643, 671, 769, 781, 827, 923, 973, 1103, 1117, 1171, 1327, 1333, 1361, 1393, 1399, 1481, 1493, 1537, 1549, 1561, 1619, 1649, 1823
OFFSET
1,2
LINKS
EXAMPLE
37 is a member as 37337 and 3373 are both prime.
MATHEMATICA
Select[Range[2000], PrimeQ[FromDigits @ Join[(d = IntegerDigits[#]), {3}, d]] && PrimeQ[FromDigits @ Join[{3}, d, {3}]] &] (* Amiram Eldar, Dec 07 2019 *)
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