A306905 a(n) = A306898(n)/2.

1, 4, 6, 16, 20, 48, 70, 160, 270, 560, 1034, 2160, 4108, 8344, 16440, 33088, 65552, 131688, 262162, 525440, 1048740, 2099240, 4194326, 8393184, 16777300, 33562672, 67109418, 134234464, 268435484, 536904960, 1073741854, 2147549824, 4294969404

Offset: 1

Author

Michael De Vlieger and N. J. A. Sloane, Mar 15 2019

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..3322

Crossrefs

Cf. A000013, A306898.

Programs

Mathematica

Table[DivisorSum[n, 2^#*EulerPhi[2 n/#] &]/2, {n, 33}] (* Michael De Vlieger, Dec 01 2019 *)

PARI

a(n) = sumdiv(n, d, 2^(n/d-1)*eulerphi(2*d)); \\ Seiichi Manyama, Jul 14 2023

Formula

a(n) = n * A000013(n). - Seiichi Manyama, Jul 14 2023