Editing Repunit (section)

== Demlo numbers ==
[[D. R. Kaprekar]] has defined Demlo numbers as concatenation of a left, middle and right part, where the left and right part must be of the same length (up to a possible leading zero to the left) and must add up to a repdigit number, and the middle part may contain any additional number of this repeated digit.<ref>{{harvs|nb|last=Kaprekar|year1=1938a|year2=1938b}}, {{Harvnb|Gunjikar|Kaprekar|1939}}</ref> 
They are named after [[Demlo]] railway station (now called [[Dombivli railway station|Dombivili]]) 30 miles from Bombay on the then [[G.I.P. Railway]], where Kaprekar started investigating them.
He calls ''Wonderful Demlo numbers'' those of the form 1, 121, 12321, 1234321, ..., 12345678987654321. The fact that these are the squares of the repunits has led some authors to call Demlo numbers the infinite sequence of these,<ref>{{MathWorld |title= Demlo Number |urlname=DemloNumber |ref=none}}</ref> 1, 121, 12321, ..., 12345678987654321, 1234567900987654321, 123456790120987654321, ..., {{OEIS|id=A002477}}, although one can check these are not Demlo numbers for ''p'' = 10, 19, 28, ...