



 
Hi Heather, These are called triangular numbers
If you go to the Quandaries and Queries page and use the Quick Search to search for the term triangular numbers you will see some previous questions we have answered on these numbers. You might find them all interesting but the one that answers your question is our response to a question by Stuart. Harley Weston  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 