text: Icosihenagonal Number | C # program to find nth Icosihenagonal number ; Function to find Icosihenagonal number ; Formula to calculate nth Icosihenagonal number ; Driver Code
code: using System ; class GFG { static int Icosihenagonal_num ( int n ) { return ( 19 * n * n - 17 * n ) / 2 ; } public static void Main ( ) { int n = 3 ; Console . Write ( Icosihenagonal_num ( n ) + " STRNEWLINE " ) ; n = 10 ; Console . Write ( Icosihenagonal_num ( n ) + " STRNEWLINE " ) ; } }