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 A326990 #36 Jan 11 2025 10:34:55
%S A326990 0,0,3,0,5,3,7,0,12,5,11,3,13,7,23,0,17,12,19,5,31,11,23,3,30,13,39,7,
%T A326990 29,23,31,0,47,17,47,12,37,19,55,5,41,31,43,11,77,23,47,3,56,30,71,13,
%U A326990 53,39,71,7,79,29,59,23,61,31,103,0,83,47,67,17,95,47,71,12,73,37,123,19,95,55,79,5
%N A326990 Sum of odd divisors of n that are greater than 1.
%C A326990 Also sum of nonpowers of 2 dividing n, divided the sum of powers of 2 dividing n.
%C A326990 a(n) = 0 iff n is a power of 2.
%C A326990 a(n) = n iff n is an odd prime.
%C A326990 First differs from A284233 at a(15).
%H A326990 Harvey P. Dale, <a href="/A326990/b326990.txt">Table of n, a(n) for n = 1..1000</a>
%F A326990 a(n) = A000593(n) - 1.
%F A326990 a(n) = (A000203(n) - A038712(n))/A038712(n).
%F A326990 a(n) = A326988(n)/A038712(n).
%e A326990 For n = 18 the divisors of 18 are [1, 2, 3, 6, 9, 18]. The sum of odd divisors of 18 that are greater than 1 is 3 + 9 = 12, so a(18) = 12. On the other hand, there are four divisors of 18 that are not powers of 2, they are [3, 6, 9, 18], and the sum of them is 3 + 6 + 9, 18 = 36. Also there are two divisors of 18 that are powers of 2, they are [1, 2], and the sum of them is 1 + 2 = 3. Then we have that 36/3 = 12, so a(18) = 12.
%t A326990 Table[Total[Select[Rest[Divisors[n]],OddQ]],{n,80}] (* _Harvey P. Dale_, Jan 11 2025 *)
%o A326990 (Magma) sol:=[]; m:=1; for n in [1..80] do v:=[d:d in Divisors(n)|d gt 1 and IsOdd(d)]; if #v ne 0 then sol[m]:=&+v; m:=m+1; else sol[m]:=0; m:=m+1; end if; end for; sol; // _Marius A. Burtea_, Aug 24 2019
%Y A326990 Cf. A000079, A000203, A000593, A038712, A057716, A065091, A069283 (Number), A284233, A326988, A326989.
%K A326990 nonn
%O A326990 1,3
%A A326990 _Omar E. Pol_, Aug 24 2019