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: #include <bits/stdc++.h> NEW_LINE using namespace std ; int Tridecagonal_num ( int n ) { return ( 11 * n * n - 9 * n ) / 2 ; } int main ( ) { int n = 3 ; cout << Tridecagonal_num ( n ) << endl ; n = 10 ; cout << Tridecagonal_num ( n ) << endl ; return 0 ; }