A227417 - OEIS

%I #18 Jun 13 2015 00:54:42

%S 1,5,8,2,6,9,3,7,10,4,8,11,5,9,12,6,10,13,7,11,14,8,12,15,9,13,16,10,

%T 14,17,11,15,18,12,16,19,13,17,20,14,18,21,15,19,22,16,20,23,17,21,24,

%U 18,22,25,19,23,26,20,24,27,21,25,28,22,26,29,23,27,30,24

%N Integer triples a(3n-2) = n, a(3n-1) = n+4, and a(3n) = n+7.

%C Major chords: If we were to number the musical notes in increasing order of frequency starting with the key of C, we would get C as 1, C# as 2, D as 3 and so on until the next octave. My sequence comprises the keys that would make major chord sounds; for example, a C major chord would be 1,5,8, and a C# major chord would be 2,6,9, and so on.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,1,-1).

%F G.f.: x*(1+4*x+3*x^2-7*x^3)/((-1+x)^2 *(1+x+x^2)).

%t Flatten[Table[{n, n + 4, n + 7}, {n, 33}]] (* _T. D. Noe_, Sep 03 2013 *)

%K nonn,easy

%O 1,2

%A _Yash Deshpande_, Jul 11 2013