1 = 1
3 = 1 + 2
6 = 1 + 2 + 3
10 = 1 + 2 + 3 + 4
15 = 1 + 2 + 3 + 4 + 5
this is how we work out triangular numbers. It is the number of dots that when drawn form a triangle
The formula for the nth triangular number is n(n+1)/2
Chat with our AI personalities