

A227417


Integer triples a(3n2) = n, a(3n1) = n+4, and a(3n) = n+7.


0



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, 14, 17, 11, 15, 18, 12, 16, 19, 13, 17, 20, 14, 18, 21, 15, 19, 22, 16, 20, 23, 17, 21, 24, 18, 22, 25, 19, 23, 26, 20, 24, 27, 21, 25, 28, 22, 26, 29, 23, 27, 30, 24
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OFFSET

1,2


COMMENTS

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.


LINKS

Table of n, a(n) for n=1..70.
Index entries for linear recurrences with constant coefficients, signature (1,0,1,1).


FORMULA

G.f.: x*(1+4*x+3*x^27*x^3)/((1+x)^2 *(1+x+x^2)).


MATHEMATICA

Flatten[Table[{n, n + 4, n + 7}, {n, 33}]] (* T. D. Noe, Sep 03 2013 *)


CROSSREFS

Sequence in context: A119420 A134469 A238166 * A260061 A199379 A198844
Adjacent sequences: A227414 A227415 A227416 * A227418 A227419 A227420


KEYWORD

nonn,easy


AUTHOR

Yash Deshpande, Jul 11 2013


STATUS

approved



