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 A285895 #34 Dec 30 2022 03:55:41
%S A285895 1,3,4,6,6,12,8,12,13,18,12,24,14,24,24,24,18,39,20,36,32,36,24,48,31,
%T A285895 42,40,48,30,72,32,48,48,54,48,78,38,60,56,72,42,96,44,72,78,72,48,96,
%U A285895 57,93,72,84,54,120,72,96,80,90,60,144,62,96,104,96,84,144,68
%N A285895 Sum of divisors d of n such that n/d is not congruent to 0 mod 4.
%H A285895 Seiichi Manyama, <a href="/A285895/b285895.txt">Table of n, a(n) for n = 1..10000</a>
%F A285895 G.f.: Sum_{k>=1} k*x^k*(1 + x^k + x^(2*k))/(1 - x^(4*k)). - _Ilya Gutkovskiy_, Sep 12 2019
%F A285895 a(n) = A050460(n) + A002131(n/2) + A050464(n), where A002131(.)=0 for non-integer argument. - _R. J. Mathar_, May 25 2020
%F A285895 From _Amiram Eldar_, Oct 30 2022: (Start)
%F A285895 Multiplicative with a(2^e) = 3*2^(e-1) and a(p^e) = (p^(e+1)-1)/(p-1) if p > 2.
%F A285895 Sum_{k=1..n} a(k) ~ c * n^2, where c = 5*Pi^2/64 = 0.7710628... . (End)
%F A285895 Dirichlet g.f.: zeta(s)*zeta(s-1)*(1-1/4^s). - _Amiram Eldar_, Dec 30 2022
%e A285895 The divisors of 8 are 1, 2, 4, and 8. 8/1 == 0 (mod 4) and 8/2 == 0 (mod 4). Hence, a(8) = 4 + 8 = 12.
%t A285895 f[p_, e_] := If[p == 2, 3*2^(e-1), (p^(e+1)-1)/(p-1)]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, Oct 30 2022 *)
%o A285895 (PARI) a(n)=sumdiv(n, d, if(n/d%4, d, 0)); \\ _Andrew Howroyd_, Jul 20 2018
%Y A285895 Cf. A002131 (k=2), A078708 (k=3), this sequence (k=4), A285896 (k=5).
%Y A285895 Cf. A002131, A050460, A050464.
%K A285895 nonn,mult
%O A285895 1,2
%A A285895 _Seiichi Manyama_, Apr 28 2017