Driver code
static public void Main ( ) { long n = 6 ; Console . WriteLine ( n + " th ▁ centered " + " ▁ octagonal ▁ number ▁ : ▁ " + cen_octagonalnum ( n ) ) ; n = 11 ; Console . WriteLine ( n + " th ▁ centered " + " ▁ octagonal ▁ number ▁ : ▁ " + cen_octagonalnum ( n ) ) ; } }