Think triangular numbers.
Do a web search.
Hello all, thanks for your help. Attatched is a table showing a pattern to find the "nth" figure, depending on what the "n" figure is. Of course the pattern is that nth=whatever the previous nth was+n, but the question asks to give the formula to find each nth, and what I stated would not be an acceptable answer. What is the mathematical formula to find each nth? Thank you all for your help, have a great day.