OFFSET
0,3
LINKS
Wikipedia, Permutation
MAPLE
b:= proc(s, x, y) option remember; `if`(s={}, 1, add(
`if`((x=0 or abs(x-j)<=4) and (y=0 or abs(y-j)<=3),
b(s minus {j}, y, j), 0), j=s))
end:
a:= n-> b({$1..n}, 0$2):
seq(a(n), n=0..20);
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Alois P. Heinz, Nov 03 2020
STATUS
approved