Palindromic Triangular Numbers/Mistake 1

Source Work

1986: David Wells: Curious and Interesting Numbers:

The Dictionary

$15$

Mistake

There are $40$ palindromic triangular numbers below $10^7$.

Correction

There are in fact $22$ of them below $10^7$.

The $23$rd one is $35 \, 133 \, 153$, which is $3 \cdotp 5 \times 10^7$.

In David Wells: Curious and Interesting Numbers (2nd ed.), this statement has been removed.

Sources

• 1986: David Wells: Curious and Interesting Numbers ... (previous) ... (next): $15$