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 A339049 #10 Dec 21 2020 07:33:09 %S A339049 1,2,2,2,2,2,2,4,4,2,4,2,2,2,2,6,4,4,2,4,4,6,4,2,2,8,2,4,4,2,2,12,8,2, %T A339049 4,2,8,4,4,2,2,2,16,4,8,12,12,4,4,4,2,2,8,2,6,4,8,4,12,8,2,8,2,18,12, %U A339049 2,12,4,4,2,4,4,8,4,2,10,8,12,6 %N A339049 a(n) = A000010(2*n + 1)/A053447(n), for n >= 0. %C A339049 This gives the number of seeds S(2*n+1) = a(n) needed for the complete quadrupling system modulo 2*n + 1 given in A339046. %F A339049 a(n) = phi(2*n + 1)/A053447(n), for n >= 0, with phi = A000010. %t A339049 Array[EulerPhi[#]/MultiplicativeOrder[4, #] &[2 # + 1] &, 61, 0] (* _Michael De Vlieger_, Dec 13 2020 *) %o A339049 (PARI) a(n) = eulerphi(2*n+1)/znorder(Mod(4, 2*n+1)); \\ _Michel Marcus_, Dec 15 2020 %Y A339049 Cf. A000010, A053447, A339046. %K A339049 nonn,easy %O A339049 0,2 %A A339049 _Wolfdieter Lang_, Dec 13 2020