A171820 Numbers n such that the n-th prime is of the form 3k + 1/2 +- 1/2.

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

Offset: 1

Author

Juri-Stepan Gerasimov, Dec 19 2009

Keywords

• nonn
• less

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

Examples

			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.
		

Crossrefs

Cf. A000027, A000040, A007645, A091177.

Programs

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