Remove nth frames of a gif (remove a frame every n frames)

I've recorded a .gif of the screen with ffmpeg. I've used gifsicle and imagemagick to compress it a bit, but it's still to big. My intent is making it small by removing, say, a frame every 2 frames, so that the total count of frames will be halved. I couldn't find a way to do it, neither with gifsicle nor with imagemagick. man pages didn't help. **How can I remove a frame from a .gif animation every n frames?**