Add the previous triangular number. For example 6 + 3 or 10 + 6 or 15 + 10. Using some algebera: n(n+1)/2 + (n-1)n/2 = n-squared
Chat with our AI personalities
144 is a square number, not a triangular number.
1, the first triangular number, is also a square.
It is 13 squared, but it's not a triangular number
A number, t, is a triangular number if (1 + 8t) is a square of an odd number.
69