Le crayon a papier is also called a crayon alone right because i have seen just crayon being used more then le crayon a papier

Hi Ayanah, 

You might be interested in this answer from the Académie française -

https://www.academie-francaise.fr/domitille-b#:~:text=L'Acad%C3%A9mie%20r%C3%A9pond,si%20les%20autres%20sont%20correctes.

 

For me 'un crayon' is just short for a pencil.

Bonne Continuation !