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%I #10 Feb 07 2017 14:30:04
%S 2,4,6,8,11,12,14,18,19,21,22,25,27,29,31,34,36,37,38,42,44,46,47,48,
%T 50,53,58,59,61,63,65,67,68,70,73,74,75,78,80,82,84,85,88,90,93,95,99,
%U 100,101,105,106,110,111,112,114,115,117,121,122,125,127,129,130,131,133
%N Numbers n such that the n-th prime is of the form 3k + 1/2 +- 1/2.
%C Numbers n such that the n-th prime is a generalized Cuban prime (A007645). A171820 UNION A091177 = A000027.
%C Essentially the same as A091178. - _R. J. Mathar_, Jan 28 2010
%e 2 is in the sequence because 2nd prime = 3*1 + 1/2 - 1/2;
%e 4 is in the sequence because 4th prime = 3*2 + 1/2 + 1/2.
%o (PARI) list(lim)=my(v=List(),n); forprime(p=2,, if(n++>lim, return(Vec(v))); if(p%3<2, listput(v,n))) \\ _Charles R Greathouse IV_, Feb 07 2017
%Y Cf. A000027, A000040, A007645, A091177.
%K nonn,less
%O 1,1
%A _Juri-Stepan Gerasimov_, Dec 19 2009
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