What is the nth term

[quakenstein]

Hey guys, trying to figure out the nth term of a sequence 8, 15, 34, 65, 108...
At first sight, i thought i know it, but when i treid to write it down, i found out i was wrong. It should be something really easy, but i´m blind or something

 

[quakenstein]

ok, found it

 

[Otis]

Hi quakenstein. Is it quadratic? You may post your work, for the benefit of future readers.

Also, please show your thoughts or efforts in the future, when starting threads. Thanks!



[imath]\;[/imath]