Here is a bodyweight exercise that incorporates a pushup and a plank. Plank pushups are a great way to strengthen the core and upper body. 

To start, get into a plank position on your forearms, keep the navel pulled in, shoulders down and back and spine long. Walk yourself up by pressing one palm into the mat followed by the other hand. Lower back down one side at a time and alternate sides to do it again. This exercise can also be done in a kneeling position. To add a bit of a challenge you can add a full pushup with a clap.

Have fun and please watch your form!

https://youtu.be/jJlngx6n8Ak