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 A378996 #14 Dec 14 2024 05:25:36 %S A378996 2,4,1,8,5,3,7,16,6,10,11,2,13,1,5,32,17,36,19,4,7,11,23,12,50,26,9,7, %T A378996 29,5,31,64,11,34,35,24,37,19,13,40,41,3,43,22,5,23,47,8,98,100,17,52, %U A378996 53,27,55,14,19,58,59,1,61,31,21,128,65,11,67,68,23,5,71,144,73,74,25,38,77,39,79,80,54,82,83,7 %N A378996 Denominator of sigma(2*n)/(2*n). %H A378996 Antti Karttunen, <a href="/A378996/b378996.txt">Table of n, a(n) for n = 1..32769</a> %H A378996 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>. %F A378996 a(n) = A017666(2*n). %F A378996 a(n) = 2*n / A378994(n). %t A378996 a[n_] := Denominator[DivisorSigma[-1, 2*n]]; Array[a, 100] (* _Amiram Eldar_, Dec 14 2024 *) %o A378996 (PARI) A378996(n) = denominator(sigma(2*n)/(2*n)); %Y A378996 Even bisection of A017666. %Y A378996 Topmost row of array A341606. %Y A378996 Cf. A378994, A378995 (numerators). %Y A378996 Cf. also A336849. %K A378996 nonn,frac,easy %O A378996 1,1 %A A378996 _Antti Karttunen_, Dec 13 2024