A174100 Numbers k such that both 2*k + 1 and 6*k + 1 are prime.

1, 2, 3, 5, 6, 11, 18, 21, 23, 26, 30, 33, 35, 51, 56, 63, 68, 81, 83, 90, 95, 96, 105, 125, 128, 131, 135, 138, 146, 153, 156, 165, 168, 173, 186, 200, 215, 216, 221, 230, 233, 243, 245, 261, 270, 278, 293, 296, 300, 336, 338, 363, 375, 378, 380, 398

Offset

1,2

Links

Table of n, a(n) for n=1..56.

Example

a(1)=1 because 1*2 + 1 = 3 (a prime) and 1*6 + 1 = 7 (also a prime).

Mathematica

Select[Range[400], PrimeQ[2#+1]&&PrimeQ[6#+1]&]  (* Harvey P. Dale, Jan 17 2011 *)

Crossrefs

Cf. A002476, A065091.

Sequence in context: A112598 A346721 A078913 * A359599 A114339 A339308

Adjacent sequences: A174097 A174098 A174099 * A174101 A174102 A174103

Keyword

nonn

Author

Juri-Stepan Gerasimov, Mar 07 2010

Extensions

Corrected (118 removed, 132 replaced by 131) by R. J. Mathar, Apr 20 2010

Name edited by Jon E. Schoenfield, May 19 2019

Status

approved