Squares with No More than 2 Distinct Digits/Historical Note

Historical Note on Squares with No More than 2 Distinct Digits

Writing in $1997$, David Wells reports in his Curious and Interesting Numbers, 2nd ed. attributes the largest known square numbers which has no more than $2$ distinct (non-zero) digits, $6\,661\,661\,161$, to Yoshigahara.

It is assumed that this is the renowned puzzler Nobuyuki Yoshigahara.

Sources

• 1997: David Wells: Curious and Interesting Numbers (2nd ed.) ... (previous) ... (next): $6,661,661,161$