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 A364869 #18 Aug 21 2023 12:01:04 %S A364869 1,2,3,4,5,6,7,10,11,12,13,16,17,18,20,21,23,25,26,27,30,32,33,35,37, %T A364869 38,40,45,46,47,48,51,52,55,56,58,61,62,63,66,68,70,72,73,76,77,81,83, %U A364869 87,88,90,91,95,96,100,101,102,103,105,107,110,112,115,118,121,122,123 %N A364869 Numbers k such that 6*k+1 is the norm of an Eisenstein prime. %C A364869 Numbers k such that 6*k+1 is a prime or the square of a prime congruent to 5 modulo 6. %C A364869 If p is an Eisenstein prime of norm 6*a(n)+1 (there are two up to association if a(n) is a prime, one if a(n) is the square of a prime), then for any Eisenstein integer x, we have x^a(n) == 0, 1, w, w^2, -1, -w or -w^2 (mod p), where w = (1+sqrt(-3))/2 is a primitive sixth root of unity. %H A364869 Jianing Song, <a href="/A364869/b364869.txt">Table of n, a(n) for n = 1..10000</a> %F A364869 a(n) = (A055664(n+2) - 1)/6. %e A364869 4 is a term since 6*4+1 is the norm of the Eisenstein prime 5. %o A364869 (PARI) isA364869(n) = isA055664(6*n+1) \\ See A055664 for its program %Y A364869 Cf. A055664, A364868. %Y A364869 Contains 4*A024702 as a subsequence. %K A364869 nonn,easy %O A364869 1,2 %A A364869 _Jianing Song_, Aug 11 2023