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%I #28 Jun 27 2022 21:23:59
%S 2,3,6,8,9,11,14,15,20,21,24,27,29,33,38,39,42,47,50,54,59,63,66,68,
%T 69,71,75,80,83,84,90,95,96,101,102,114,116,119,128,131,132,138,143,
%U 149,150,152,156,161,167,168,171,177,180,186,189,194,200,201,206,207,209
%N Numbers k such that the concatenation '2',k,'3' is prime.
%C This sequence is infinite, a consequence of the Prime Number Theorem in arithmetic progressions. - _Charles R Greathouse IV_, Sep 26 2012
%H Vincenzo Librandi, <a href="/A032711/b032711.txt">Table of n, a(n) for n = 1..1000</a>
%e 8 and 21 are in the sequence because 283 and 2213 are primes.
%t v={};Do[If[PrimeQ[FromDigits[Join[{2},IntegerDigits[n],{3}]]], v=Append[v,n]],{n, 260}];v (* _Farideh Firoozbakht_, Jun 15 2003 *)
%t Select[Range[210],PrimeQ[FromDigits[Join[{2},IntegerDigits[#],{3}]]]&] (* _Harvey P. Dale_, May 02 2012 *)
%o (PARI) for( n=1,300, isprime(eval(Str(2,n,3))) & print1(n",")) \\ _M. F. Hasler_, Mar 18 2008
%Y Cf. A083677, A083966, A083969, A092117.
%K nonn,base
%O 1,1
%A _Patrick De Geest_, May 15 1998
%E Merged with data from duplicate entry A092114. - _M. F. Hasler_, Mar 18 2008
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