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 A359204 #13 Aug 27 2023 16:40:18
%S A359204 1,9,49,289,1281,7041,28673,147969,602113,2951169,11534337,57876481,
%T A359204 218103809,1056997377,4113563649,19394592769,73014444033,354385657857,
%U A359204 1305670057985,6210524807169,23571585826817,108851659538433,404620279021569,1942025331015681
%N A359204 a(n) = Sum_{d|n} (n/d) * 4^(n-d).
%F A359204 G.f.: Sum_{k>=1} x^k/(1 - (4 * x)^k)^2.
%t A359204 a[n_] := DivisorSum[n, 4^(n-#)*n/# &]; Array[a, 24] (* _Amiram Eldar_, Aug 27 2023 *)
%o A359204 (PARI) a(n) = sumdiv(n, d, n/d*4^(n-d));
%o A359204 (PARI) my(N=30, x='x+O('x^N)); Vec(sum(k=1, N, x^k/(1-(4*x)^k)^2))
%Y A359204 Cf. A000203, A080267, A115607, A359203.
%Y A359204 Cf. also A359112.
%K A359204 nonn,easy
%O A359204 1,2
%A A359204 _Seiichi Manyama_, Dec 20 2022