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 A183072 #13 Feb 18 2019 09:57:31
%S A183072 6,10,14,15,26,30,34,38,43,51,62,65,79,85,86,93,95,122,129,130,133,
%T A183072 158,170,193,254,255,301,311,331,349,389,445,557,577,579,631,647,1103,
%U A183072 1167
%N A183072 Positive integers k such that 2^k - 1 is composite and each of its prime divisors has the form 4j + 3.
%C A183072 Needed factorizations are in the Cunningham Project.
%H A183072 S. S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>.
%F A183072 A183076(n) = 2^a(n) - 1.
%e A183072 6 is in this sequence because 2^6 - 1 = 3^2 * 7, and 3 and 7 have the form 4j + 3.
%t A183072 c4j3Q[n_]:=Module[{c=2^n-1},CompositeQ[c]&&AllTrue[(#-3)/4&/@ FactorInteger[ c] [[All,1]],IntegerQ]]; Select[Range[650],c4j3Q] (* Requires Mathematica version 10 or later *) (* The program takes a long time to run *) (* _Harvey P. Dale_, Sep 23 2018 *)
%Y A183072 Cf. A000043, A136003, A183071, A183073, A183074.
%Y A183072 Cf. A000668, A136005, A183075, A183076, A183077, A183078.
%K A183072 nonn,hard,more
%O A183072 1,1
%A A183072 _Stuart Clary_, Dec 23 2010
%E A183072 a(38)-a(39) from _Amiram Eldar_, Feb 18 2019