A168063 Numbers k such that exactly two of {k-2, k-1, k+1, k+2} are primes.

1, 3, 5, 6, 9, 12, 15, 18, 21, 30, 39, 42, 45, 60, 69, 72, 81, 99, 102, 105, 108, 111, 129, 138, 150, 165, 180, 192, 195, 198, 225, 228, 231, 240, 270, 279, 282, 309, 312, 315, 348, 351, 381, 399, 420, 432, 441, 459, 462, 465, 489, 501, 522, 570, 600, 615, 618

Offset: 1

Author

Juri-Stepan Gerasimov, Nov 18 2009

Keywords

• nonn
• easy

Comments

Essentially the same as A014574 U A087679. - Charles R Greathouse IV, May 25 2011

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A014574, A087679.

Programs

Mathematica

Select[Range[700],Count[#+{-2,-1,1,2},?PrimeQ]==2&] (* _Harvey P. Dale, Jan 24 2014 *)

Extensions

Corrected (105 inserted, 609 removed) by R. J. Mathar, Jun 04 2010