A306905 - OEIS

%I #15 Jul 14 2023 09:02:10

%S 1,4,6,16,20,48,70,160,270,560,1034,2160,4108,8344,16440,33088,65552,

%T 131688,262162,525440,1048740,2099240,4194326,8393184,16777300,

%U 33562672,67109418,134234464,268435484,536904960,1073741854,2147549824,4294969404

%N a(n) = A306898(n)/2.

%H Michael De Vlieger, <a href="/A306905/b306905.txt">Table of n, a(n) for n = 1..3322</a>

%F a(n) = n * A000013(n). - _Seiichi Manyama_, Jul 14 2023

%t Table[DivisorSum[n, 2^#*EulerPhi[2 n/#] &]/2, {n, 33}] (* _Michael De Vlieger_, Dec 01 2019 *)

%o (PARI) a(n) = sumdiv(n, d, 2^(n/d-1)*eulerphi(2*d)); \\ _Seiichi Manyama_, Jul 14 2023

%Y Cf. A000013, A306898.

%K nonn

%O 1,2

%A _Michael De Vlieger_ and _N. J. A. Sloane_, Mar 15 2019