Generate a series of vampire numbers between a given lower and upper bound. Limited by the allowed values for the long datatype. For the definition of vampire numbers, see the following description lifted from the related wikipedia article:
In number theory, a vampire number (or true vampire number) is a composite natural number with an even number of digits, that can be factored into two natural numbers each with half as many digits as the original number and not both with trailing zeroes, where the two factors contain precisely all the digits of the original number, in any order, counting multiplicity. The first vampire number is 1260 = 21 × 60.