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 A306905 #15 Jul 14 2023 09:02:10
%S A306905 1,4,6,16,20,48,70,160,270,560,1034,2160,4108,8344,16440,33088,65552,
%T A306905 131688,262162,525440,1048740,2099240,4194326,8393184,16777300,
%U A306905 33562672,67109418,134234464,268435484,536904960,1073741854,2147549824,4294969404
%N A306905 a(n) = A306898(n)/2.
%H A306905 Michael De Vlieger, <a href="/A306905/b306905.txt">Table of n, a(n) for n = 1..3322</a>
%F A306905 a(n) = n * A000013(n). - _Seiichi Manyama_, Jul 14 2023
%t A306905 Table[DivisorSum[n, 2^#*EulerPhi[2 n/#] &]/2, {n, 33}] (* _Michael De Vlieger_, Dec 01 2019 *)
%o A306905 (PARI) a(n) = sumdiv(n, d, 2^(n/d-1)*eulerphi(2*d)); \\ _Seiichi Manyama_, Jul 14 2023
%Y A306905 Cf. A000013, A306898.
%K A306905 nonn
%O A306905 1,2
%A A306905 _Michael De Vlieger_ and _N. J. A. Sloane_, Mar 15 2019