N=4 solutions=2 first=2 4 1 3
N=5 solutions=10 first=1 3 5 2 4
N=6 solutions=4 first=2 4 6 1 3 5
N=7 solutions=40 first=1 3 5 7 2 4 6
N=8 solutions=92 first=1 5 8 6 3 7 2 4
