2ndpentagonalnumber

<-- Enter pentagonal number statement
  

Calculate pentagonal number 2

The formula for pentagonal number n is as follows
Pn  =  n(3n - 1)
  2

Given n = 2, we have:
P2  =  2(3(2) - 1)
  2

P2  =  2(6 - 1)
  2

P2  =  2(5)
  2

P2  =  10
  2

P2 = 5