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%I #19 Dec 14 2024 05:25:40
%S 3,7,2,15,9,7,12,31,13,21,18,5,21,2,12,63,27,91,30,9,16,21,36,31,93,
%T 49,20,15,45,14,48,127,24,63,72,65,57,35,28,93,63,8,66,45,13,42,72,21,
%U 171,217,36,105,81,70,108,31,40,105,90,3,93,56,52,255,126,28,102,135,48,12,108,403,111,133,62,75,144,98,120
%N Numerator of sigma(2*n)/(2*n).
%H Antti Karttunen, <a href="/A378995/b378995.txt">Table of n, a(n) for n = 1..32769</a>
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F a(n) = A017665(2*n).
%F a(n) = A062731(n) / A378994(n).
%F Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k)/A378996(k) = 5*Pi^2/24 (= 10 * A245058). - _Amiram Eldar_, Dec 14 2024
%t a[n_] := Numerator[DivisorSigma[-1, 2*n]]; Array[a, 100] (* _Amiram Eldar_, Dec 14 2024 *)
%o (PARI) A378995(n) = numerator(sigma(2*n)/(2*n));
%Y Even bisection of A017665.
%Y Topmost row of array A341605.
%Y Cf. A062731, A245058, A378994, A378996 (denominators).
%Y Cf. also A341525.
%K nonn,frac,easy
%O 1,1
%A _Antti Karttunen_, Dec 13 2024