Why 1 is called as triangular number.
These are the first 100 triangular numbers:
The sequence of the triangular numbers comes from the natural numbers (and zero), if you always add the next number:
1You can illustrate the name triangular number by the following drawing:
The general representation of a triangular number is dn= 1 + 2 + 3 + 4 +...+ (n-2) + (n-1) + n,
where n is a natural number.