text: Tridecagonal Number | C # program to find N - th tridecagonal number ; Function to find N - th tridecagonal number ; Formula to calculate nth tridecagonal number ; Driver Code
code: using System ; class GFG { static int Tridecagonal_num ( int n ) { return ( 11 * n * n - 9 * n ) / 2 ; } public static void Main ( String [ ] args ) { int n = 3 ; Console . Write ( Tridecagonal_num ( n ) + " STRNEWLINE " ) ; n = 10 ; Console . Write ( Tridecagonal_num ( n ) + " STRNEWLINE " ) ; } }