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 A326126 #12 Mar 21 2024 05:46:24
%S A326126 0,1,1,6,1,6,1,13,12,8,1,25,1,10,9,30,1,37,1,37,11,14,1,54,30,16,37,
%T A326126 49,1,42,1,61,15,20,13,90,1,22,17,80,1,54,1,73,73,26,1,121,56,91,21,
%U A326126 85,1,114,17,106,23,32,1,153,1,34,97,126,19,78,1,109,27,74,1,193,1,40,121,121,19,90,1,181,120,44,1,203,23,46,33,158,1,224,21
%N A326126 Sum of all other divisors of n except the squarefree part of n: a(n) = sigma(n) - A007913(n).
%H A326126 Antti Karttunen, <a href="/A326126/b326126.txt">Table of n, a(n) for n = 1..16384</a>
%H A326126 Antti Karttunen, <a href="/A326126/a326126.txt">Data supplement: n, a(n) computed for n = 1..65537</a>.
%H A326126 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A326126 a(n) = A000203(n) - A007913(n).
%F A326126 Sum_{k=1..n} a(k) ~ c * n^2, where c = Pi^2/20 = 0.4934802... . - _Amiram Eldar_, Mar 21 2024
%t A326126 f1[p_, e_] := (p^(e + 1) - 1)/(p - 1); f2[p_, e_] := p^Mod[e, 2]; a[n_] := Module[{f = FactorInteger[n]}, Times @@ f1 @@@ f - Times @@ f2 @@@ f]; a[1] = 0; Array[a, 100] (* _Amiram Eldar_, Mar 21 2024 *)
%o A326126 (PARI) A326126(n) = (sigma(n)-core(n));
%Y A326126 Cf. A000203, A007913, A326127, A326128, A326129.
%Y A326126 Cf. also A326053, A326061, A326142.
%K A326126 nonn
%O A326126 1,4
%A A326126 _Antti Karttunen_, Jun 09 2019