Driver Code
$ n = 3 ; echo $ n , " th ▁ centered ▁ octadecagonal ▁ " . " number ▁ : ▁ " , center_octadecagon_num ( $ n ) ; echo " STRNEWLINE " ; $ n = 13 ; echo $ n , " th ▁ centered ▁ octadecagonal ▁ " . " number ▁ : ▁ " , center_octadecagon_num ( $ n ) ; ? >