OFFSET
7,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 7..460
MAPLE
b:= proc(u, o, t, c) option remember; `if`(c>2, 0, `if`(u+o=0,
`if`(c=2, 1, 0), add(b(u-j, o-1+j, [2, 2, 4, 2][t], c), j=1..u)+
add(b(u+j-1, o-j, [1, 3, 1, 3][t], c+`if`(t=4, 1, 0)), j=1..o)))
end:
a:= n-> b(0, n, 1, 0);
seq(a(n), n=7..25); # Alois P. Heinz, Nov 02 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 02 2015
STATUS
approved