A090263 Numbers n such that the strings n3n and 3n3 are both prime.
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
Examples
37 is a member as 37337 and 3373 are both prime.
Links
- Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Range[2000], PrimeQ[FromDigits @ Join[(d = IntegerDigits[#]), {3}, d]] && PrimeQ[FromDigits @ Join[{3}, d, {3}]] &] (* Amiram Eldar, Dec 07 2019 *)
Extensions
More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004