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 A183073 #18 Feb 18 2019 06:04:59 %S A183073 2,3,5,7,13,17,19,31,43,61,79,89,107,127,193,311,331,349,389,521,557, %T A183073 577,607,631,647,1103 %N A183073 Prime numbers p such that each prime divisor of 2^p - 1 has the form 4j + 3. %C A183073 The exponents of the Mersenne primes (A000043) are contained in this sequence. %C A183073 Needed factorizations are in the Cunningham Project. %C A183073 Also in the sequence are 1279, 2203, 2281, 2909, 3217, 4253. - _Amiram Eldar_, Feb 18 2019 %H A183073 S. S. Wagstaff, Jr., <a href="http://homes.cerias.purdue.edu/~ssw/cun/index.html">The Cunningham Project</a>. %F A183073 A183077(n) = 2^a(n) - 1. %e A183073 43 is in this sequence because 2^43 - 1 = 431 * 9719 * 2099863, and each of those primes has the form 4j + 3. %t A183073 Select[Prime[Range[30]],And@@(IntegerQ[(#-3)/4]&/@Transpose[ FactorInteger[ 2^#-1]][[1]])&] (* Increase the value of Range to increase the number of terms generated, but processing times grow very quickly as the value increases. *)(* _Harvey P. Dale_, Jan 01 2013 *) %Y A183073 Cf. A000043, A136003, A183071, A183072, A183074. %Y A183073 Cf. A000668, A136005, A183075, A183076, A183077, A183078. %K A183073 nonn,hard,more %O A183073 1,1 %A A183073 _Stuart Clary_, Dec 23 2010 %E A183073 a(26) from _Amiram Eldar_, Feb 18 2019