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%I #18 Mar 21 2019 02:38:53
%S 0,3,6,13,22,40,55,88,118,163,205,280,334,436,517,625,733,901,1018,
%T 1225,1381,1591,1786,2083,2287,2617,2887,3238,3544,4006,4306,4831,
%U 5239,5749,6205,6817,7267,8005,8572,9280,9880,10780,11374,12361
%N Number of colors that can be mixed with up to n units of yellow, blue, red.
%H T. D. Noe, <a href="/A048134/b048134.txt">Table of n, a(n) for n = 0..1000</a>
%F a(n) = number of triples (i, j, k) with 1 <= i+j+k <= n and gcd(i, j, k) = 1.
%F Cumulative sums of A048240(k) for k>0.
%e a(2)=6: primary and secondary colors (Y^1, B^1, R^1, Y^1*B^1, Y^1*R^1, B^1*R^1).
%t Accumulate[ Table[ Sum[ MoebiusMu[n/d]*(d + 1)*(d + 2)/2, {d, Divisors[n]}], {n, 0, 43}]] (* _Jean-François Alcover_, Jul 16 2012, after _Vladeta Jovovic_ *)
%Y Two colors gives A005728.
%Y Cf. A048240, A048241.
%K nonn,nice,easy
%O 0,2
%A _Jurjen N.E. Bos_
%E More terms from Robin Trew (trew(AT)hcs.harvard.edu).
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