How are frames in 59.94 drop-frame timecode dropped? The pattern for dropping frames in 29.97 drop-frame SMPTE timecode is well documented (2 frames at every minute except when minute is a multiple of 10).

I was wondering how it works with 59.94 fps drop-frame timecode? I guess it needs to be twice the amount of frames dropped, but what is the exact pattern?
Apparently, the frames are dropped at the same cadence, but with double frequency.

From FFmpeg's timecode drop function,

if (fps == 30) {
    drop_frames = 2;
    frames_per_10mins = 17982;
} else if (fps == 60) {
    drop_frames = 4;
    frames_per_10mins = 35964;
} 
....
d = framenum / frames_per_10mins;
m = framenum % frames_per_10mins;

return framenum + 9*drop_frames*d + drop_frames*((m - drop_frames)/(frames_per_10mins/10));


and the string is

ff = framenum % fps;
ss = framenum / fps      % 60;
mm = framenum / (fps*60) % 60;
hh = framenum / (fps*3600) % 24;