(In reply to
First thoughts by TomM)
Yeah, that about all I could eliminate 'logically'. But, as you say:
a) Position 5 must be "5"
b) Positions 4 and 8 must be "2" and "6" in some order
c) Positions 2 and 6 must then be "4" and "8" in some order
d) Positions 1, 3, 7 and 9 must be "1", "3", "7" and "9" in some order
This only leaves us with 1 * 2 * 2 * 12 combinations, or 48 possibilities.
It's very simple to then run through those and find the solution is "381654729"