OFFSET
4,1
LINKS
Alois P. Heinz, Table of n, a(n) for n = 4..472
MAPLE
b:= proc(u, o, t) option remember; series(`if`(u+o=0, x^t,
add(b(u+j-1, o-j, irem(t+1, 2)), j=1..o)+
add(b(u-j, o+j-1, 0)*x^t, j=1..u)), x, 3)
end:
a:= n-> coeff(b(n, 0$2), x, 2):
seq(a(n), n=4..30);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 25 2018
STATUS
approved