A173136 - OEIS

%I #5 Sep 01 2017 10:58:06

%S 1,27,33,35,39,45,49,55,57,63,65,81,87,91,95,105,111,115,117,119,121,

%T 125,129,147,153,155,159,165,169,175,177,183,187,189,195,201,205,209,

%U 215,217,219,221,225,243,245,249,255,273,279,289,297,299,301,303,315

%N Odd nonprimes n such that exactly one of 2n-1 and 2n+1 is prime.

%H Harvey P. Dale, <a href="/A173136/b173136.txt">Table of n, a(n) for n = 1..1000</a>

%e a(1)=1 because 2*1-1=1 is nonprime and 2*1+1=3 is prime.

%t Select[Range[1,341,2],!PrimeQ[#]&&Total[Boole[PrimeQ[2 #+{1,-1}]]]==1&] (* _Harvey P. Dale_, Sep 01 2017 *)

%Y Cf. A014076, A172458.

%K nonn,easy,less

%O 1,2

%A _Juri-Stepan Gerasimov_, Feb 10 2010

%E Corrected at 3 or more places by _R. J. Mathar_, Mar 09 2010