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A306906 a(n) = A306899(n)/6. 1

%I

%S 1,2,6,8,15,30,49,96,189,360,693,1416,2743,5516,10980,21952,43707,

%T 87642,174781,349920,699216,1398804,2796225,5594112,11184875,22372376,

%U 44739810,89484080,178956999,357926040,715827913,1431677824,2863313640

%N a(n) = A306899(n)/6.

%H Michael De Vlieger, <a href="/A306906/b306906.txt">Table of n, a(n) for n = 1..3323</a>

%t Table[DivisorSum[n, (2^# - (-1)^#) EulerPhi[3 n/#] &]/6, {n, 33}] (* _Michael De Vlieger_, Dec 01 2019 *)

%o (PARI) a(n) = sumdiv(n, d, (2^d - (-1)^d)*eulerphi(3*n/d))/6; \\ _Michel Marcus_, Mar 16 2019

%Y Cf. A306899.

%K nonn

%O 1,2

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

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Last modified August 1 10:13 EDT 2021. Contains 346385 sequences. (Running on oeis4.)