OFFSET
4,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 4..175
EXAMPLE
a(4) = 1: o1.2o
. .....
. o3.4o
MAPLE
T:= proc(n, k) option remember; `if`(k<0 or k>n, 0, `if`(n=0, 1,
add(binomial(n-1, i)*T(n-1-i, k-1)*ceil(i!/2), i=0..n-k)))
end:
a:= n-> T(n, 4):
seq (a(n), n=4..25);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 23 2012
STATUS
approved