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 A245776 #19 Sep 08 2022 08:46:09 %S A245776 0,-1,1,-5,13,-1,33,1,14,7,97,-1,141,25,43,101,253,5,321,37,313,85, %T A245776 481,1,532,127,569,8,781,27,897,323,299,235,1033,53,1293,301,1297,11, %U A245776 1597,83,1761,179,173,457,2113,133,2230,971,771,529,2701,163,2737,34,2929,751,3361,11,3597,865,1115 %N A245776 Numerator of (n/tau(n) - sigma(n)/n). %C A245776 Numerator of (n/A000005(n) - A000203(n)/n). %C A245776 See A245777 - denominator of (n/tau(n) - sigma(n)/n). %H A245776 Michael De Vlieger, <a href="/A245776/b245776.txt">Table of n, a(n) for n = 1..10000</a> %F A245776 a(n)/A245777(n) < 1 for numbers n in A245779. %F A245776 a(n)/A245777(n) is an integer for numbers n in A245778. %F A245776 a(n) = 1 for n = 3, 8 and 24. %F A245776 a(n) < 0 for n = 2, 4, 6 and 12. %e A245776 For n = 9; a(9) = numerator(9/tau(9) - sigma(9)/9) = numerator(9/3 - 13/9) = numerator(14/9) = 14. %t A245776 a245776[n_Integer] := %t A245776 Map[Numerator[#/DivisorSigma[0, #] - DivisorSigma[1, #]/#] &, %t A245776 Range[n]]; a245776[63] (* _Michael De Vlieger_, Aug 07 2014 *) %o A245776 (Magma) [Numerator((n/(#[d: d in Divisors(n)]))-(SumOfDivisors(n)/n)): n in [1..1000]] %o A245776 (PARI) vector(150, n, numerator(n/numdiv(n) - sigma(n)/n)) \\ _Derek Orr_, Aug 01 2014 %Y A245776 Cf. A000005, A000203, A245777, A245778, A245779, A245782. %K A245776 sign,frac %O A245776 1,4 %A A245776 _Jaroslav Krizek_, Aug 01 2014