The Nth Triangular Number is the sum of the first N natural numbers. Triangular number sequence is 0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171......
Formula for Triangular Numbers Tn = n ( n + 1 ) / 2.
Lets see an example : T4 = 1 + 2 + 3 + 4 = 4 ( 4 + 1 ) / 2
Which comes out to be 10. Therefore T4 = 10.
Enter Value of N to find the Nth Triangle Number