A339965 - OEIS

%I #15 Jan 07 2023 13:05:43

%S 1,1,1,7,1,12,1,5,13,18,1,28,1,8,3,31,1,39,1,2,16,36,1,12,31,14,10,56,

%T 1,72,1,21,24,54,4,91,1,20,7,90,1,96,1,28,39,72,1,124,57,31,18,98,1,

%U 24,9,40,40,90,1,168,1,32,13,127,14,144,1,42,48,144,1,195,1,38,31,20,16,168,1,62,121,126,1,224,54,44

%N a(n) = sigma(n) / gcd(sigma(n),n+1).

%H Antti Karttunen, <a href="/A339965/b339965.txt">Table of n, a(n) for n = 1..10080</a>

%H Antti Karttunen, <a href="/A339965/a339965.txt">Data supplement: n, a(n) computed for n = 1..65537</a>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%F a(n) = A000203(n) / A339964(n).

%F a(n) = numerator(sigma(n)/(n+1)). - _Michel Marcus_, Jan 07 2023

%t Table[DivisorSigma[1, n]/GCD[DivisorSigma[1, n], n + 1], {n, 80}] (* _Wesley Ivan Hurt_, Oct 10 2021 *)

%o (PARI) A339965(n) = sigma(n)/(gcd(sigma(n),n+1));

%Y Cf. A000203, A339964, A339966 (denominators).

%Y Cf. A017665.

%Y Cf. also A160595.

%K nonn,frac,easy

%O 1,4

%A _Antti Karttunen_, Dec 25 2020