Number series problems...what comes next?

[misterbill]

Greetings: I'm working with "Marcy's Dots" problems. I have number series
6 12 20 30 42 56 and am struggling with a way to explain more clearly how to solve problems like these...any help out there???

 

[pka]

Go to this site:
http://www.research.att.com/~njas/sequences/index.html