6thpentagonalnumber

<-- Enter pentagonal number statement
  

Calculate pentagonal number 6

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

Given n = 6, we have:
P6  =  6(3(6) - 1)
  2

P6  =  6(18 - 1)
  2

P6  =  6(17)
  2

P6  =  102
  2

P6 = 51