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 A367509 #12 Nov 21 2023 09:40:23
%S A367509 3,34,370,7267,161294,4960812,170861562,7019201348,322728071069,
%T A367509 16705828227476,952809758091074,59628239376008854,4052555153020570590,
%U A367509 297587425607933152700,23465266173840431204452,1978033864507607364591749,177482997121587371955312038
%N A367509 a(n) = Sum_{d|n} (2*d+1)^n.
%H A367509 Seiichi Manyama, <a href="/A367509/b367509.txt">Table of n, a(n) for n = 1..351</a>
%F A367509 a(n) = Sum_{k=0..n} 2^k * binomial(n,k) * sigma_k(n).
%o A367509 (PARI) a(n) = sumdiv(n, d, (2*d+1)^n);
%Y A367509 Cf. A163190, A367510.
%K A367509 nonn
%O A367509 1,1
%A A367509 _Seiichi Manyama_, Nov 21 2023