Driver Code
int main ( ) { long int n = 3 ; cout << n << " th ▁ centered ▁ octadecagonal ▁ number ▁ : ▁ " << center_octadecagon_num ( n ) ; cout << endl ; n = 13 ; cout << n << " th ▁ centered ▁ octadecagonal ▁ number ▁ : ▁ " << center_octadecagon_num ( n ) ; return 0 ; }