Tetrahedral Numbers which are Sum of 2 Tetrahedral Numbers/Mistake

Source Work

 * The Dictionary
 * $680$
 * $680$


 * The Dictionary
 * $680$
 * $680$

Mistake

 * $680$ is the smallest tetrahedral number to be the sum of two tetrahedral numbers: $680 = 120 + 560$.

Correction
In fact it is the $2$nd.

The smallest is $20$:
 * $20 = 10 + 10$

However, it would be correct to state this as:
 * $680$ is the smallest tetrahedral number to be the sum of two distinct tetrahedral numbers: $680 = 120 + 560$.