186911domain: NAppears in sequencesComposite numbers not divisible by 5 which in base 5 contain their largest proper factor as a substring.at n=30A063889Composite numbers k such that if k = a U b (where U denotes concatenation) then a' + b' = k', where a', b' and k' are the arithmetic derivatives of a, b and k.at n=25A239724