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 A153443 #6 Jun 02 2025 01:17:01 %S A153443 3,5,11,13,17,43,241,257,331,683,2731,5419,43691,61681,65537,174763, %T A153443 2796203,15790321,18837001,22366891,715827883,4278255361,4562284561, %U A153443 77158673929,1133836730401,2932031007403,4363953127297 %N A153443 Aurifeuillian primes of the form 2^k+1. %C A153443 Take an irreducible real factor of x^k+1 and substitute x=2. If the result is a prime then it belongs in this sequence. For example for k=5 the polynomial x^5+1=(x+1)(x^4-x^3+x^2-x+1) and substituting x->2 in (x^4-x^3+x^2-x+1) we get the prime number 11. So 11 is a term. [Clarified by _N. J. A. Sloane_, Jul 03 2020] %Y A153443 A061442. %K A153443 nonn %O A153443 1,1 %A A153443 _Artur Jasinski_, Dec 26 2008