Now let "a, b, d, e" be odd numbers while "c" and "f" be even numbers. Given the odd bone numbers at our disposal: ± 5, ± 7, ± 9, and ± 11, their differences range from "D" = { ± 2, ± 4, ± 6} while their sums range from "S" = {± 12, ± 14, ± 16, ± 18, ± 20}. It is also useful to have a table of their sum and differences for later reference. Now, given the corner cells ("u", "v"), we can check its admissibility by checking if the sums "u" + "v" + "c" and "v" + "u*" + "f" fall within the set "D" or "S". The admissibility of the corner numbers is a necessary but not a sufficient condition for the solution to exist.