9thheptagonalnumber

<-- Enter heptagonal number statement
  

Calculate heptagonal number 9

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

Given n = 9, we have:
H9  =  9(5(9) - 3)
  2

H9  =  9(45 - 3)
  2

H9  =  9(42)
  2

H9  =  378
  2

H9 = 189