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A048134
Number of colors that can be mixed with up to n units of yellow, blue, red.
5
0, 3, 6, 13, 22, 40, 55, 88, 118, 163, 205, 280, 334, 436, 517, 625, 733, 901, 1018, 1225, 1381, 1591, 1786, 2083, 2287, 2617, 2887, 3238, 3544, 4006, 4306, 4831, 5239, 5749, 6205, 6817, 7267, 8005, 8572, 9280, 9880, 10780, 11374, 12361
OFFSET
0,2
FORMULA
a(n) = number of triples (i, j, k) with 1 <= i+j+k <= n and gcd(i, j, k) = 1.
Cumulative sums of A048240(k) for k>0.
EXAMPLE
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).
MATHEMATICA
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 *)
CROSSREFS
Two colors gives A005728.
Sequence in context: A361276 A211870 A239987 * A058397 A174369 A308747
KEYWORD
nonn,nice,easy
EXTENSIONS
More terms from Robin Trew (trew(AT)hcs.harvard.edu).
STATUS
approved