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 A318059 #17 Apr 04 2024 07:55:39 %S A318059 1,2,7,2,12,14,15,3,14,39,28,14,24,30,4,2,39,28,42,24,3,91,60,7,32,48, %T A318059 10,30,72,13,63,13,124,60,124,28,60,84,40,117,96,6,84,56,56,195,124, %U A318059 14,80,64,65,171,120,20,39,45,62,117,168,8,96,126,10,2,224,403,126,78,84,403 %N A318059 a(n) is the numerator of sigma(sigma(n))/n. %H A318059 Robert Israel, <a href="/A318059/b318059.txt">Table of n, a(n) for n = 1..10000</a> %F A318059 For n=2, sigma(sigma(n)) = 4, so a(2) = 2. %e A318059 Fractions begin with 1, 2, 7/3, 2, 12/5, 14/3, 15/7, 3, 14/9, 39/10, 28/11, 14/3, ... %p A318059 seq(numer((numtheory:-sigma@@2)(n)/n),n=1..100); # _Robert Israel_, Aug 14 2018 %t A318059 a[n_] := Numerator[DivisorSigma[1, DivisorSigma[1, n]]/n]; Array[a, 100] (* _Amiram Eldar_, Apr 04 2024 *) %o A318059 (PARI) a(n) = numerator(sigma(sigma(n))/n); %Y A318059 Cf. A000203 (sigma), A051027. %Y A318059 Cf. A098223 (when denominator is 1), A318060 (denominator). %K A318059 nonn,frac %O A318059 1,2 %A A318059 _Michel Marcus_, Aug 14 2018