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 A171820 Numbers n such that the n-th prime is of the form 3k + 1/2 +- 1/2. 1
 2, 4, 6, 8, 11, 12, 14, 18, 19, 21, 22, 25, 27, 29, 31, 34, 36, 37, 38, 42, 44, 46, 47, 48, 50, 53, 58, 59, 61, 63, 65, 67, 68, 70, 73, 74, 75, 78, 80, 82, 84, 85, 88, 90, 93, 95, 99, 100, 101, 105, 106, 110, 111, 112, 114, 115, 117, 121, 122, 125, 127, 129, 130, 131, 133 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n such that the n-th prime is a generalized Cuban prime (A007645). A171820 UNION A091177 = A000027. Essentially the same as A091178. - R. J. Mathar, Jan 28 2010 LINKS EXAMPLE 2 is in the sequence because 2nd prime = 3*1 + 1/2 - 1/2; 4 is in the sequence because 4th prime = 3*2 + 1/2 + 1/2. PROG (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 CROSSREFS Cf. A000027, A000040, A007645, A091177. Sequence in context: A195873 A073140 A256342 * A193879 A226722 A187414 Adjacent sequences:  A171817 A171818 A171819 * A171821 A171822 A171823 KEYWORD nonn,less AUTHOR Juri-Stepan Gerasimov, Dec 19 2009 STATUS approved

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Last modified October 14 16:48 EDT 2019. Contains 328022 sequences. (Running on oeis4.)