OFFSET
1,4
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..3324
Silvana Ramaj, New Results on Cyclic Compositions and Multicompositions, Master's Thesis, Georgia Southern Univ., 2021. See p. 48.
MATHEMATICA
Table[DivisorSum[n, (2^# + 2 (-1)^#) EulerPhi[n/#] &]/6, {n, 38}] (* Michael De Vlieger, Mar 18 2019 *)
PROG
(PARI) a(n) = sumdiv(n, d, (2^d + 2*(-1)^d)*eulerphi(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