OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..55
FORMULA
a(n) = A262372(2n,n).
EXAMPLE
a(2) = 8: (2134,2134), (2143,2143), (2314,2314), (2314,2413), (2341,2341), (2413,2314), (2413,2413), (2431,2431).
MAPLE
b:= proc(u, o, h) option remember; `if`(u+o=0, 1,
add(add(b(u-j, o+j-1, h+i-1), i=1..u+o-h), j=1..u)+
add(add(b(u+j-1, o-j, h-i), i=1..h), j=1..o))
end:
a:= n-> `if`(n=0, 1, b(n-1, n, n)):
seq(a(n), n=0..15);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Sep 20 2015
STATUS
approved