Tetrahedral Numbers which are Sum of 2 Tetrahedral Numbers/Mistake

Source Work

1986: David Wells: Curious and Interesting Numbers:

The Dictionary

$680$

1997: David Wells: Curious and Interesting Numbers (2nd ed.):

The Dictionary

$680$

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: $680 = 120 + 560$.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $680$
• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $680$