A048241 - OEIS

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A048241

Number of colors that can be mixed with n >= 0 units of yellow, blue, red.

1, 4, 7, 14, 23, 41, 56, 89, 119, 164, 206, 281, 335, 437, 518, 626, 734, 902, 1019, 1226, 1382, 1592, 1787, 2084, 2288, 2618, 2888, 3239, 3545, 4007, 4307, 4832, 5240, 5750, 6206, 6818, 7268, 8006, 8573, 9281, 9881, 10781, 11375, 12362

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OFFSET

0,2

LINKS

T. D. Noe, Table of n, a(n) for n = 0..1000

FORMULA

a(n) = number of triples (i, j, k) with 0 <= i+j+k <= n and gcd(i, j, k) = 1.

a(n) = A048134(n)+1. - T. D. Noe, Jan 16 2007

EXAMPLE

a(2)=7: white, primary and secondary colors (null, 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}]] + 1 (* Jean-François Alcover, Oct 16 2013, after T. D. Noe *)

CROSSREFS

Cf. A048134, A048240.

Sequence in context: A146417 A008370 A291877 * A003404 A139025 A221107

Adjacent sequences: A048238 A048239 A048240 * A048242 A048243 A048244

KEYWORD

nonn,easy,nice

AUTHOR

Jurjen N.E. Bos, N. J. A. Sloane, Robin Trew (trew(AT)hcs.harvard.edu)

STATUS

approved