OFFSET
1,1
COMMENTS
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).
Also Euler-Jacobi pseudoprimes to base 3 that are congruent to 1 (mod 6).
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Eric Weissteins's World of Mathematics, Eisenstein Integer.
Wikipedia, Eisenstein integer.
MATHEMATICA
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
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Feb 28 2020
STATUS
approved