I was given a question on number patterns. The queston states tha I must keep adding one table to increase the amount of seatings by keeping it in a square formation. I need to giv a general formula but I am struggling with the sequence

Hmm. Not sure just what's wanted, but recall that

(n+1)^2 = n^2+2n+1
so, if after each increase there are

n^2+2n tables, then you need to add 1 more to keep it a perfect square.

So, the sequence would be

3,7,15,24,35,...