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 A165972 #6 Oct 01 2015 10:51:52
%S A165972 1,4,6,10,12,16,18,22,28,30,36,40,42,46,52,58,60,66,70,72,78,82,88,96,
%T A165972 100,102,106,108,112,126,130,136,138,148,150,156,162,166,172,178,180,
%U A165972 190,192,196,198,210,222,226,228,232,238,240,250,256,262,268,270,276
%N A165972 Nonprimes k such that the sum of the smallest and largest divisor of k is prime.
%C A165972 n-(-1)^n is prime.
%C A165972 Largest nonprime<prime(n+1) or largest nonprime<n-th odd prime. [From _Juri-Stepan Gerasimov_, Oct 29 2009]
%F A165972 A006093 \ {2}.
%e A165972 k=1 is in the sequence because 1+1=2 is prime. k=4 is in the sequence because 1+4=5 is prime.
%t A165972 Select[Range[300],!PrimeQ[#]&&With[{d=Divisors[#]},PrimeQ[d[[1]]+ d[[-1]]]]&] (* _Harvey P. Dale_, Oct 01 2015 *)
%Y A165972 Cf. A000040, A006093, A018252.
%K A165972 nonn,less
%O A165972 1,2
%A A165972 _Juri-Stepan Gerasimov_, Oct 02 2009, Oct 14 2009
%E A165972 Entries checked by _R. J. Mathar_, Oct 10 2009