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A083031
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Numbers that are congruent to {0, 3, 7} mod 12.
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15
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0, 3, 7, 12, 15, 19, 24, 27, 31, 36, 39, 43, 48, 51, 55, 60, 63, 67, 72, 75, 79, 84, 87, 91, 96, 99, 103, 108, 111, 115, 120, 123, 127, 132, 135, 139, 144, 147, 151, 156, 159, 163, 168, 171, 175, 180, 183, 187, 192, 195, 199, 204, 207, 211, 216, 219
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OFFSET
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1,2
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COMMENTS
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Key-numbers of the pitches of a minor common chord on a standard chromatic keyboard, with root = 0.
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LINKS
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FORMULA
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G.f.: x^2*(3 + 4*x + 5*x^2)/((1 + x + x^2)*(1 - x)^2). - R. J. Mathar, Oct 08 2011
a(n) = a(n-1) + a(n-3) - a(n-4) for n > 4.
a(n) = (12*n - 14 - cos(2*n*Pi/3) + sqrt(3)*sin(2*n*Pi/3))/3.
a(3k) = 12k - 5, a(3k-1) = 12k - 9, a(3k-2) = 12k - 12. (End)
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MAPLE
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MATHEMATICA
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Select[Range[0, 400], MemberQ[{0, 3, 7}, Mod[#, 12]] &] (* Wesley Ivan Hurt, Jun 14 2016 *)
LinearRecurrence[{1, 0, 1, -1}, {0, 3, 7, 12}, 100] (* Jianing Song, Sep 22 2018 *)
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PROG
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(Magma) [n : n in [0..300] | n mod 12 in [0, 3, 7]]; // Wesley Ivan Hurt, Jun 14 2016
(PARI) x='x+O('x^99); concat(0, Vec(x^2*(3+4*x+5*x^2)/((1+x+x^2)*(1-x)^2))) \\ Jianing Song, Sep 22 2018
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CROSSREFS
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A guide for some sequences related to modes and chords:
Modes:
Chords:
Minor chord: this sequence
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KEYWORD
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nonn,easy
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AUTHOR
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James Ingram (j.ingram(AT)t-online.de), Jun 01 2003
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STATUS
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approved
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