3rdheptagonalnumber

<-- Enter heptagonal number statement
  

Calculate heptagonal number 3

The formula for heptagonal number n is as follows
Hn  =  n(5n - 3)
  2

Given n = 3, we have:
H3  =  3(5(3) - 3)
  2

H3  =  3(15 - 3)
  2

H3  =  3(12)
  2

H3  =  36
  2

H3 = 18