How can you tell if a table is proportional or non proportional?

I can tell by how bad it looks or by if it had a cracked spot on it that’s how I can tell if it’s non proportional

This is what i found “an explicit formula designates the nth term of the sequence, as an expression of n (where n = the term's location). it defines the sequence as a formula in terms of n. this example is an arithmetic sequence(the same number, 5, is added to each term to get to the next term).” i hope this you for what your looking for. can you plz mark me brainliest?