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 A359731 #21 Aug 14 2023 02:00:18
%S A359731 1,9,109,2057,50001,1493109,52706753,2147485705,99179645293,
%T A359731 5120000050009,292159150705665,18260173719523445,1240576436601868289,
%U A359731 91029559915023973833,7174453500000000050109,604462909807316734838793,54214017802982966177103873
%N A359731 a(n) = (1/2) * Sum_{d|n} (2*d)^d.
%H A359731 Seiichi Manyama, <a href="/A359731/b359731.txt">Table of n, a(n) for n = 1..351</a>
%F A359731 G.f.: Sum_{k>0} 2^(k-1) * (k * x)^k / (1 - x^k).
%t A359731 a[n_] := DivisorSum[n, (2*#)^# &] / 2; Array[a, 20] (* _Amiram Eldar_, Aug 14 2023 *)
%o A359731 (PARI) a(n) = sumdiv(n, d, (2*d)^d)/2;
%o A359731 (PARI) my(N=20, x='x+O('x^N)); Vec(sum(k=1, N, 2^(k-1)*(k*x)^k/(1-x^k)))
%Y A359731 Cf. A062796, A076723, A359732.
%K A359731 nonn,easy
%O A359731 1,2
%A A359731 _Seiichi Manyama_, Jan 12 2023