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 A289412 #20 Nov 21 2022 07:49:52 %S A289412 1,1,1,2,2,1,3,4,6,2,5,1,6,1,1,8,8,2,9,4,3,5,11,2,20,2,9,3,14,1,15,16, %T A289412 5,8,1,12,18,3,3,8,20,1,21,5,4,11,23,4,14,20,4,12,26,3,5,1,9,14,29,2, %U A289412 30,5,9,32,4,5,33,16,11,1,35,8,36,6,10,9,5,1 %N A289412 a(n) = denominator of (sigma(n) / phi(n)). %C A289412 a(n) = 1 for numbers in A020492 (balanced numbers). %H A289412 Amiram Eldar, <a href="/A289412/b289412.txt">Table of n, a(n) for n = 1..10000</a> %F A289412 a(n) = denominator of (A000203(n) / A000010(n)). %e A289412 For n = 7, sigma(7) / phi(7) = 8/6 = 4/3, a(n) = 3. %t A289412 Array[Denominator[DivisorSigma[1, #]/EulerPhi[#]] &, 78] (* _Michael De Vlieger_, Aug 19 2017 *) %o A289412 (Magma) [Denominator(SumOfDivisors(n) / EulerPhi(n)): n in[1..1000]] %o A289412 (PARI) a(n) = denominator(sigma(n)/eulerphi(n)); \\ _Michel Marcus_, Aug 21 2017 %Y A289412 Cf. A289336 (numerators). %Y A289412 Cf. A000010, A000203, A018894, A020492, A023897, A055234, A070032, A070033. %K A289412 nonn,frac %O A289412 1,4 %A A289412 _Jaroslav Krizek_, Aug 19 2017