Centered tridecagonal number | Function to find nth centered tridecagonal number ; Formula to calculate nth centered tridecagonal number ; Driver Code
< ? php function centeredTridecagonalNum ( $ n ) { return ( 13 * $ n * ( $ n - 1 ) + 2 ) / 2 ; } $ n = 3 ; echo centeredTridecagonalNum ( $ n ) ; echo " STRNEWLINE " ; $ n = 10 ; echo centeredTridecagonalNum ( $ n ) ; ? >