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 A380541 #27 Jul 07 2025 10:43:59
%S A380541 0,1,4,2,5,4,8,3,22,28,10,12,20,7,46,52,29,20,11,70,6,26,41,22,16,100,
%T A380541 34,53,12,28,14,65,68,23,148,10,52,27,166,172,89,60,190,32,196,66,35,
%U A380541 74,113,76,58,238,8,25,16,262,268,90,92,35
%N A380541 a(n) is the multiplicative order of -8 modulo prime(n); a(1) = 0 for completion.
%H A380541 Jianing Song, <a href="/A380541/b380541.txt">Table of n, a(n) for n = 1..10000</a>
%F A380541 a(n) = ord(-2,p)/gcd(ord(-2,p),3) for p != 2, where p = prime(n), and ord(a,m) is the multiplicative order of a modulo m. Note that ord(-2,p) = A337878(n) for n > 2.
%t A380541 A380541[n_] := If[n == 1, 0, MultiplicativeOrder[-8, Prime[n]]];
%t A380541 Array[A380541, 100] (* _Paolo Xausa_, Jun 29 2025 *)
%o A380541 (PARI) a(n,{k=-8}) = my(p = prime(n)); if(k%p==0, 0, znorder(Mod(k,p)))
%Y A380541 Cf. A105880 (primes having primitive root -8).
%Y A380541 Cf. bases 2..10: A014664, A062117, A082654, A211241, A211242, A211243, A211244, A211245, A002371.
%Y A380541 Cf. bases -2..-10: A337878 (if first term 1), A380482, A380531, A380532, A380533, A380540, this sequence, A380542, A385222.
%K A380541 nonn,easy
%O A380541 1,3
%A A380541 _Jianing Song_, Jun 27 2025