Firstly I want to say sorry because I have collected it from a running programming contest but I can't stop myself from knowing the system.
Please help me about finding the number of shapes after cutting v-shaped from a rectangular board.
More info in the image .
if the v-shaped cut is 1 - total shapes will be 2.
if the v-shaped cut is 2 - total shapes will be 7.
Hint:
No of pieces after $n$-cuts can be given by: $$a_n=a_{n-1}+4n-3$$ where $a_1=2$.