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 A359134 #37 Aug 14 2023 01:59:16
%S A359134 1,3,5,13,17,55,65,201,293,779,1025,3365,4097,12303,17781,49681,65537,
%T A359134 204547,262145,791549,1095429,3145751,4194305,12897625,16787217,
%U A359134 50331675,68788805,201591509,268435457,815505231,1073741825,3223326753,4355433957,12884901923
%N A359134 a(n) = Sum_{d|n} (2*d)^(n/d - 1).
%H A359134 Seiichi Manyama, <a href="/A359134/b359134.txt">Table of n, a(n) for n = 1..1000</a>
%F A359134 G.f.: Sum_{k>0} x^k / (1 - 2 * k * x^k).
%F A359134 If p is prime, a(p) = 1 + 2^(p-1).
%t A359134 a[n_] := DivisorSum[n, (2*#)^(n/# - 1) &]; Array[a, 30] (* _Amiram Eldar_, Aug 14 2023 *)
%o A359134 (PARI) a(n) = sumdiv(n, d, (2*d)^(n/d-1));
%o A359134 (PARI) my(N=40, x='x+O('x^N)); Vec(sum(k=1, N, x^k/(1-2*k*x^k)))
%Y A359134 Cf. A087909, A278741, A349970, A359733, A359796.
%K A359134 nonn
%O A359134 1,2
%A A359134 _Seiichi Manyama_, Jan 13 2023