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%I #8 May 05 2023 14:15:09
%S 12,17,19,22,24,26,27,29,31,32,33,34,36,37,38,39,40,41,42,43,44,45,46,
%T 47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,
%U 70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92
%N Natural numbers n such that there are s and w satisfying 0 < s < w and 2*s + 5*w = n.
%C Number of equal microtone intervals dividing a musical octave, so that it is (formally) possible to compose one octave (according to the diatonic scale) of two semi-tone-steps and five whole-tone-steps, each being a multiple of the microtone interval.
%H <a href="http://www.magnetkern.de/microtone/equal-temperament.html">Analysis of equal temperament tuning systems</a> (German language)
%e 12 = 2*1 + 5*2
%e 17 = 2*1 + 5*3
%e 19 = 2*2 + 5*3
%e 22 = 2*1 + 5*4
%e ...
%t Union[2*First[#]+5*Last[#]&/@Subsets[Range[20],{2}]] (* _Harvey P. Dale_, Mar 28 2012 *)
%o (Haskell)
%o filter (\n -> [ (s,w) | s<-[1..n], w<-[(s+1)..n], 2*s+5*w == n ] /= []) [1..]
%K nonn
%O 1,1
%A Jan Behrens (jbe-oeis(AT)magnetkern.de), Jul 17 2009
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