Driver function
int main ( ) { long int n = 4 ; cout << n << " th ▁ Icosidigonal ▁ number ▁ : " << icosidigonal_num ( n ) ; cout << endl ; n = 8 ; cout << n << " th ▁ Icosidigonal ▁ number : " << icosidigonal_num ( n ) ; return 0 ; }