It's a common approximation(*) of the Fourier transform, used to estimate frequency components in time series data.
It was an Easter egg for Master Po, who may have missed implied time when I said rhythm.
(*)The even more common one is to use Euler's and just directly evaluate from there, but it was just easier to copy from wikipedia than spell out the eq'n. A great deal of what I've done and published started with that eq'n.
(Stated for Po's benefit, just to beat him to that punch.
Ok Bob - once again 1,1,1,2,__ or 1,1,2,1,3,1,4,__
I guess time is running out.