Kind of tailored to the orders of magnitude approach of the test suite; complexity would have to increase significantly if you split the intervals say [10000 50000] instead of [1e4 1e5-1].

Everything is perfect in this code.

this is not really a general solution, perhaps you could add more complicated cases in the testsuite? for example pandigital_nb(2200,4000)==10, pandigital_nb(250,40000)==98, pandigital_nb(35327,43854637)==23030

I hesitated to add tests that I can't solve by myself.

I see, check solution 443089, that should be a general and relatively fast solution