8thpentagonalnumber

<-- Enter pentagonal number statement
  

Calculate pentagonal number 8

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

Given n = 8, we have:
P8  =  8(3(8) - 1)
  2

P8  =  8(24 - 1)
  2

P8  =  8(23)
  2

P8  =  184
  2

P8 = 92