\begin{definition}[Definition:Kaprekar Number/Sequence]
The sequence of Kaprekar numbers begins:
:$1, 9, 45, 55, 99, 297, 703, 999, 2223, 2728, 4879, 4950, 5050, 5292, 7272, 7777, 9999, 17344, \ldots$
{{OEIS|A006886}}
Some sources do not include such numbers as $4879$ and $5292$:
:$1, 9, 45, 55, 99, 297, 703, 999, 2223, 2728, 4950, 5050, 7272, 7777, 9999, 17344, \ldots$
where the $2$nd of the $2$ parts begins with one or more leading zeroes:
:$4879^2 = 23 \, 804 \, 641 \to 238 + 04641 = 4879$
:$5292^2 = 28 \, 005 \, 264 \to 28 + 005264 = 5292$
{{OEIS|A053816}}
\end{definition}