OFFSET
1,2
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..3323
MATHEMATICA
Table[DivisorSum[n, (2^# - (-1)^#) EulerPhi[3 n/#] &]/6, {n, 33}] (* Michael De Vlieger, Dec 01 2019 *)
PROG
(PARI) a(n) = sumdiv(n, d, (2^d - (-1)^d)*eulerphi(3*n/d))/6; \\ Michel Marcus, Mar 16 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Michael De Vlieger and N. J. A. Sloane, Mar 15 2019
STATUS
approved