Triangular Numbers

Who remembers triangular numbers from maths classes at school? 1; 3; 6; 10; 15; 21....... and so on.

I thought these Liquorice Allsorts were an ideal way to illustrate the concept of triangular numbers. I don't really know what function they perform in the real world but as a number sequence (or should that be a series - can't remember the mathematical difference) triangular numbers are one of my favourite.

Olympus E-3; Zuiko 35mm; ISO 400; f3.5; 1/60s. FL-50R on camera.