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 A346877 #32 Sep 29 2024 12:05:58
%S A346877 0,1,1,1,4,1,1,9,1,1,11,1,6,13,1,1,15,13,1,17,1,1,33,1,8,21,1,17,23,1,
%T A346877 1,41,19,1,27,1,1,49,19,1,40,1,23,33,1,21,35,25,1,57,1,1,87,1,1,41,1,
%U A346877 29,65,25,12,45,31,1,47,1,27,105,1,1,51,25,35,81,1,1,81,37
%N A346877 Sum of the divisors, except for the largest, of the n-th odd number.
%C A346877 Sum of aliquot divisors (or aliquot parts) of the n-th odd number.
%C A346877 a(n) has a symmetric representation.
%F A346877 a(n) = A001065(2*n-1).
%F A346877 a(n) = A057427(n-1) + A346879(n).
%F A346877 G.f.: Sum_{k>=0} (2*k + 1) * x^(3*k + 2) / (1 - x^(2*k + 1)). - _Ilya Gutkovskiy_, Aug 20 2021
%F A346877 Sum_{k=1..n} a(k) = (Pi^2/8 - 1)*n^2 + O(n*log(n)). - _Amiram Eldar_, Mar 17 2024
%e A346877 For n = 5 the 5th odd number is 9 and the divisors of 9 are [1, 3, 9] and the sum of the divisors of 9 except for the largest is 1 + 3 = 4, so a(5) = 4.
%t A346877 a[n_] := DivisorSigma[1, 2*n - 1] - 2*n + 1; Array[a, 100] (* _Amiram Eldar_, Aug 20 2021 *)
%t A346877 Total[Most[Divisors[#]]]&/@Range[1,161,2] (* _Harvey P. Dale_, Sep 29 2024 *)
%o A346877 (Python)
%o A346877 from sympy import divisors
%o A346877 def a(n): return sum(divisors(2*n-1)[:-1])
%o A346877 print([a(n) for n in range(1, 79)]) # _Michael S. Branicky_, Aug 20 2021
%o A346877 (PARI) a(n) = sigma(2*n-1) - (2*n-1); \\ _Michel Marcus_, Aug 20 2021
%Y A346877 Bisection of A001065.
%Y A346877 Partial sums give A347153.
%Y A346877 Cf. A000203, A005408, A008438, A057427, A153485, A237593, A245092, A244049, A326123, A346869, A346878, A346879, A347154.
%K A346877 nonn,easy
%O A346877 1,5
%A A346877 _Omar E. Pol_, Aug 20 2021