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%I #27 Dec 14 2021 15:11:58
%S 1,3,5,7,9,10,13,15,16,17,20,23,24,26,28,30,32,33,35,39,40,41,43,45,
%T 49,51,52,54,55,56,57,60,62,64,66,69,71,72,76,77,79,81,83,86,87,89,91,
%U 92,94,96,97,98,102,103,104,107,108,109,113,116,118,119,120,123
%N Numbers m such that the m-th prime is of the form 3*k-1.
%C A003627 indexed by A000040.
%C The asymptotic density of this sequence is 1/2 (by Dirichlet's theorem). - _Amiram Eldar_, Feb 28 2021
%H Amiram Eldar, <a href="/A091177/b091177.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = k such that A000040(k) = A003627(n).
%t PrimePi/@Select[3Range[0,250]-1,PrimeQ] (* _Harvey P. Dale_, Apr 26 2011 *)
%t Select[Range[150],IntegerQ[(Prime[#]+1)/3]&] (* _Harvey P. Dale_, Dec 14 2021 *)
%o (PARI) a091177(limit)={my(m=0);forprime(p=2,prime(limit),m++;if(p%3==2,print1(m,", ")))};
%o a091177(123) \\ _Hugo Pfoertner_, Aug 03 2021
%Y Cf. A003627 (primes of the form 3*k-1), A024893, A087370, A088879.
%Y A133677 is another version.
%K nonn,easy
%O 1,2
%A _Ray Chandler_, Dec 26 2003
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