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A090263 Numbers n such that the strings n3n and 3n3 are both prime. 5

%I

%S 1,37,41,53,59,79,83,119,133,151,179,197,223,241,263,283,299,349,361,

%T 377,427,461,553,559,593,599,637,643,671,769,781,827,923,973,1103,

%U 1117,1171,1327,1333,1361,1393,1399,1481,1493,1537,1549,1561,1619,1649,1823

%N Numbers n such that the strings n3n and 3n3 are both prime.

%H Daniel Starodubtsev, <a href="/A090263/b090263.txt">Table of n, a(n) for n = 1..10000</a>

%e 37 is a member as 37337 and 3373 are both prime.

%t Select[Range[2000], PrimeQ[FromDigits @ Join[(d = IntegerDigits[#]), {3}, d]] && PrimeQ[FromDigits @ Join[{3}, d, {3}]] &] (* _Amiram Eldar_, Dec 07 2019 *)

%Y Cf. A090262, A090264, A090265.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Nov 28 2003

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

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Last modified January 16 00:05 EST 2021. Contains 340195 sequences. (Running on oeis4.)