Recommended models for sequence classification on toy synthetic datasets

I have a couple of synthetically generated tasks e.g., addition, subtraction etc.
I have tried different models so far but nothing seems to work, meaning solving the actual task.

Can you suggest what would be the bests model for these kind of tasks?
I have tried pretty much everything I could think of but most of of the models seem to not work (apart from one or two)

Can I use models for sequence classification for these tasks and if so could you provide a simple minimal working example?

Can you describe your task and language more precisely? Sequence classification can work to some extent to classify something. For a working example of sequence classification, see the following link. Text classification