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 A380540 #27 Jul 07 2025 10:43:52
%S A380540 1,2,4,0,5,12,16,6,11,14,30,18,40,3,46,13,58,60,33,35,24,39,82,88,96,
%T A380540 100,102,53,54,7,63,130,68,138,37,75,52,81,166,172,89,12,5,24,49,198,
%U A380540 105,74,226,228,116,119,240,250,256,131,268,270,69,20
%N A380540 a(n) is the multiplicative order of -7 modulo prime(n); a(4) = 0 for completion.
%H A380540 Jianing Song, <a href="/A380540/b380540.txt">Table of n, a(n) for n = 1..10000</a>
%t A380540 A380540[n_] := If[n == 4, 0, MultiplicativeOrder[-7, Prime[n]]];
%t A380540 Array[A380540, 100] (* _Paolo Xausa_, Jun 29 2025 *)
%o A380540 (PARI) a(n,{k=-7}) = my(p = prime(n)); if(k%p==0, 0, znorder(Mod(k,p)))
%Y A380540 Cf. A105879 (primes having primitive root -7).
%Y A380540 Cf. bases 2..10: A014664, A062117, A082654, A211241, A211242, A211243, A211244, A211245, A002371.
%Y A380540 Cf. bases -2..-10: A337878 (if first term 1), A380482, A380531, A380532, A380533, this sequence, A380541, A380542, A385222.
%K A380540 nonn,easy
%O A380540 1,2
%A A380540 _Jianing Song_, Jun 27 2025