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 A183074 #11 Feb 18 2019 06:13:35
%S A183074 43,79,193,311,331,349,389,557,577,631,647,1103
%N A183074 Prime numbers p such that 2^p - 1 is composite and each of its prime divisors has the form 4j + 3.
%C A183074 Needed factorizations are in the Cunningham Project.
%H A183074 S. S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>.
%F A183074 A183078(n) = 2^a(n) - 1.
%e A183074 43 is in this sequence because 2^43 - 1 = 431 * 9719 * 2099863, and each of those primes has the form 4j + 3.
%t A183074 cQ[n_]:=Module[{x=2^n-1},!PrimeQ[x]&&Union[Mod[Transpose[ FactorInteger[ x]][[1]],4]]=={3}]; Select[Prime[Range[120]],cQ] (* _Harvey P. Dale_, Jun 17 2014 *)
%Y A183074 Cf. A000043, A136003, A183071, A183072, A183073.
%Y A183074 Cf. A000668, A136005, A183075, A183076, A183077, A183078.
%K A183074 nonn,hard
%O A183074 1,1
%A A183074 _Stuart Clary_, Dec 23 2010
%E A183074 a(12) from _Amiram Eldar_, Feb 18 2019