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 A380827 #24 Feb 23 2025 11:32:17 %S A380827 1,1,2,2,4,2,5,4,5,4,7,4,7,5,6,6,16,5,11,6,7,7,13,6,9,7,11,7,11,6,10, %T A380827 10,9,16,9,7,13,11,9,8,13,7,12,9,9,13,25,8,12,9,18,9,17,11,11,9,13,11, %U A380827 31,8,12,10,10,18,11,9,16,18,15,9,14,9,17,13,11,13,12,9,18,10,29 %N A380827 Least integer k such that the multiplicative group modulo n is a subgroup of the symmetric group S_k. %H A380827 Asher Gray, <a href="/A380827/b380827.txt">Table of n, a(n) for n = 1..10000</a> %H A380827 Wikipedia, <a href="http://en.wikipedia.org/wiki/Multiplicative_group_of_integers_modulo_n">Multiplicative group of integers modulo n</a> %F A380827 a(j*k) = a(j) + a(k) where j and k are coprime and both greater than 2. %F A380827 a(2j) = j where j is odd. %F A380827 a(2) = 1, a(4) = 2, a(2^k) = 2 + 2^(k-2) for k >= 3. %F A380827 a(p^k) = A008475(p-1) * p^(k-1) for odd prime p. %Y A380827 Cf. A008475, A380222, A282625. %K A380827 nonn %O A380827 1,3 %A A380827 _Asher Gray_, Feb 04 2025