This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A173136 #5 Sep 01 2017 10:58:06
%S A173136 1,27,33,35,39,45,49,55,57,63,65,81,87,91,95,105,111,115,117,119,121,
%T A173136 125,129,147,153,155,159,165,169,175,177,183,187,189,195,201,205,209,
%U A173136 215,217,219,221,225,243,245,249,255,273,279,289,297,299,301,303,315
%N A173136 Odd nonprimes n such that exactly one of 2n-1 and 2n+1 is prime.
%H A173136 Harvey P. Dale, <a href="/A173136/b173136.txt">Table of n, a(n) for n = 1..1000</a>
%e A173136 a(1)=1 because 2*1-1=1 is nonprime and 2*1+1=3 is prime.
%t A173136 Select[Range[1,341,2],!PrimeQ[#]&&Total[Boole[PrimeQ[2 #+{1,-1}]]]==1&] (* _Harvey P. Dale_, Sep 01 2017 *)
%Y A173136 Cf. A014076, A172458.
%K A173136 nonn,easy,less
%O A173136 1,2
%A A173136 _Juri-Stepan Gerasimov_, Feb 10 2010
%E A173136 Corrected at 3 or more places by _R. J. Mathar_, Mar 09 2010