1stpentagonalnumber

<-- Enter pentagonal number statement
  

Calculate pentagonal number 1

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

Given n = 1, we have:
P1  =  1(3(1) - 1)
  2

P1  =  1(3 - 1)
  2

P1  =  1(2)
  2

P1  =  2
  2

P1 = 1