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A306906 a(n) = A306899(n)/6. 0
1, 2, 6, 8, 15, 30, 49, 96, 189, 360, 693, 1416, 2743, 5516, 10980, 21952, 43707, 87642, 174781, 349920, 699216, 1398804, 2796225, 5594112, 11184875, 22372376, 44739810, 89484080, 178956999, 357926040, 715827913, 1431677824, 2863313640 (list; graph; refs; listen; history; text; internal format)
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

Cf. A306899.

Sequence in context: A049818 A066189 A278834 * A174658 A326300 A266074

Adjacent sequences:  A306903 A306904 A306905 * A306907 A306908 A306909

KEYWORD

nonn,changed

AUTHOR

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

STATUS

approved

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Last modified December 7 09:33 EST 2019. Contains 329843 sequences. (Running on oeis4.)