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 A329705 #18 Feb 16 2025 08:33:58
%S A329705 121,703,1729,1891,2821,7381,8401,8911,10585,12403,15457,15841,16531,
%T A329705 18721,19345,23521,24661,28009,29341,31621,41041,44287,46657,47197,
%U A329705 49141,50881,52633,55969,63139,63973,74593,75361,79003,82513,87913,88573,93961,97567,105163
%N A329705 Composite numbers k such that (1 - w)^(k-1) == 1 (mod k) in the ring of Eisenstein integers (w = (-1 + sqrt(3)*i)/2).
%C A329705 w = exp(2*Pi*i/3) = (-1 + sqrt(3)*i)/2, where i is the imaginary unit, is a unit in the ring of Eisenstein integers (usually denoted by the Greek letter omega).
%C A329705 Also Euler-Jacobi pseudoprimes to base 3 that are congruent to 1 (mod 6).
%H A329705 Amiram Eldar, <a href="/A329705/b329705.txt">Table of n, a(n) for n = 1..10000</a>
%H A329705 Eric Weissteins's World of Mathematics, <a href="https://mathworld.wolfram.com/EisensteinInteger.html">Eisenstein Integer</a>.
%H A329705 Wikipedia, <a href="https://en.wikipedia.org/wiki/Eisenstein_integer">Eisenstein integer</a>.
%t A329705 eisProd[z1_, z2_] := {z1[[1]]*z2[[1]] - z1[[2]]*z2[[2]], z1[[1]]*z2[[2]] + z1[[2]]*z2[[1]] - z1[[2]]*z2[[2]]}; seq = {}; z = {1, 0}; Do[z = eisProd[{1, -1}, z]; If[CompositeQ[n] && And @@ Divisible[z - {1, 0}, n], AppendTo[seq, n]], {n, 2, 10^4}]; seq
%Y A329705 Intersection of A016921 and A048950.
%Y A329705 Cf. A066408, A270698.
%K A329705 nonn
%O A329705 1,1
%A A329705 _Amiram Eldar_, Feb 28 2020