Creating a video using a sequence of images and FFMPEG

I've been studying Blender for a while now and have developed a preference of saving the animations as a PNG image sequence instead of video files. Later I can load them in Blender's VSE, o kdenlive, and edit the video.

But sometimes I would rather just see how the animation is going without having to load the files again and render them into a video file.

 ffmpeg -f image2 -i %04d.png animation.mp4