OFFSET
0,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..500
MAPLE
b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
`if`(t=1, add(b(u-j, o+j-1, irem(t+1, 6)), j=1..u),
add(b(u+j-1, o-j, irem(t+1, 6)), j=1..o)))
end:
a:= n-> b(0, n, 0):
seq(a(n), n=0..35);
MATHEMATICA
b[u_, o_, t_] := b[u, o, t] = If[u + o == 0, 1, If[t == 1, Sum[b[u - j, o + j - 1, Mod[t + 1, 6]], {j, 1, u}], Sum[b[u + j - 1, o - j, Mod[t + 1, 6]], {j, 1, o}]]];
a[n_] := b[0, n, 0];
Table[a[n], {n, 0, 35}] (* Jean-François Alcover, Jul 22 2019, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Nov 15 2014
STATUS
approved
