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 A351647 #36 Oct 11 2023 03:54:16
%S A351647 0,1,1,1,1,10,1,1,10,26,1,10,1,50,35,1,1,91,1,26,59,122,1,10,26,170,
%T A351647 91,50,1,260,1,1,131,290,75,91,1,362,179,26,1,500,1,122,341,530,1,10,
%U A351647 50,651,299,170,1,820,147,50,371,842,1,260,1,962,581,1,195,1220,1,290
%N A351647 Sum of the squares of the odd proper divisors of n.
%H A351647 Seiichi Manyama, <a href="/A351647/b351647.txt">Table of n, a(n) for n = 1..10000</a>
%H A351647 <a href="/index/Su#sums_of_divisors">Index entries for sequences related to sums of divisors</a>.
%F A351647 a(n) = Sum_{d|n, d<n, d odd} d^2.
%F A351647 G.f.: Sum_{k>=1} (2*k-1)^2 * x^(4*k-2) / (1 - x^(2*k-1)). - _Ilya Gutkovskiy_, Mar 02 2022
%F A351647 From _Amiram Eldar_, Oct 11 2023: (Start)
%F A351647 a(n) = A050999(n) - n^2*A000035(n).
%F A351647 Sum_{k=1..n} a(k) ~ c * n^2, where c = (zeta(3)-1)/6 = 0.0336761505... . (End)
%e A351647 a(10) = 26; a(10) = Sum_{d|10, d<10, d odd} d^2 = 1^2 + 5^2 = 26.
%t A351647 f[2, e_] := 1; f[p_, e_] := (p^(2*e+2) - 1)/(p^2 - 1); a[1] = 0; a[n_] := Times @@ f @@@ FactorInteger[n] - If[OddQ[n], n^2, 0]; Array[a, 60] (* _Amiram Eldar_, Oct 11 2023 *)
%o A351647 (PARI) a(n) = sumdiv(n, d, if ((d%2) && (d<n), d^2)); \\ _Michel Marcus_, Mar 02 2022
%Y A351647 Sum of the k-th powers of the odd proper divisors of n for k=0..10: A091954 (k=0), A091570 (k=1), this sequence (k=2), A352031 (k=3), A352032 (k=4), A352033 (k=5), A352034 (k=6), A352035 (k=7), A352036 (k=8), A352037 (k=9), A352038 (k=10).
%Y A351647 Cf. A000035, A002117, A050999.
%K A351647 nonn,easy
%O A351647 1,6
%A A351647 _Wesley Ivan Hurt_, Mar 01 2022