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 A338891 #24 Sep 02 2025 14:12:48
%S A338891 1,21,165,1274,9435,69720,515230,3807265,28132035,207869515,
%T A338891 1535959665,11349295155,83860579775
%N A338891 a(n) is the least number k such that the average number of odd divisors of {1..k} is >= n.
%H A338891 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/OddDivisorFunction.html">Odd Divisor Function</a>.
%F A338891 a(n+1)/a(n) approaches e^2.
%e A338891 a(5) = 9435 because the average number of odd divisors of {1..9435} is >= 5.
%t A338891 m = 1; sum = 0; s = {}; Do[sum += DivisorSigma[0, k/2^IntegerExponent[k, 2]]; If[sum >= m*k, AppendTo[s, k]; m++], {k, 1, 10^6}]; s (* _Amiram Eldar_, Nov 15 2020 *)
%o A338891 (PARI) a(n) = my(s=1, k=1); while(s<k*n, k++; s=s+numdiv(k>>valuation(k, 2))); k; \\ _Michel Marcus_, Nov 14 2020
%Y A338891 Cf. A001227, A060831, A072334, A085829, A328331, A338943.
%K A338891 nonn,more,changed
%O A338891 1,2
%A A338891 _Ilya Gutkovskiy_, Nov 14 2020
%E A338891 a(11)-a(12) from _Amiram Eldar_, Nov 16 2020
%E A338891 a(13) from _Bill McEachen_, Sep 01 2025