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 A183071 #11 Feb 18 2019 06:21:20 %S A183071 1,2,3,5,6,7,10,13,14,15,17,19,26,30,31,34,38,43,51,61,62,65,79,85,86, %T A183071 89,93,95,107,122,127,129,130,133,158,170,193,254,255,301,311,331,349, %U A183071 389,445,521,557,577,579,607,631,647,1103,1167 %N A183071 Positive integers k such that each prime divisor of 2^k - 1 has the form 4j + 3. %C A183071 The exponents of the Mersenne primes (A000043) are contained in this sequence. %C A183071 Needed factorizations are in the Cunningham Project. %H A183071 S. S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>. %F A183071 A183075(n) = 2^a(n) - 1. %e A183071 6 is in this sequence because 2^6 - 1 = 3^2 * 7, and 3 and 7 have the form 4j + 3. %Y A183071 Cf. A000043, A136003, A183072, A183073, A183074. %Y A183071 Cf. A000668, A136005, A183075, A183076, A183077, A183078. %K A183071 nonn %O A183071 1,2 %A A183071 _Stuart Clary_, Dec 23 2010 %E A183071 a(53)-a(54) from _Amiram Eldar_, Feb 18 2019