Product of Two Triangular Numbers to make Square/Mistake

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Source Work

1986: David Wells: Curious and Interesting Numbers:

The Dictionary
$15$


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

The Dictionary
$15$


Mistake

For every triangular number, $T_n$, there are an infinite number of other triangular numbers, $T_m$, such that $T_n T_m$ is a square. For example, $T_3 \times T_{24} = 30^2$.


Correction

This is incorrect.


It is supposed that this is a misprint for:

$T_2 \times T_{24} = 30^2$

which is correct.


Sources