OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
MAPLE
T:= proc(n, k) option remember;
if k<3 or k=2*n then 1
else add(T(n-1, k-j), j=1..3)
fi
end:
seq(add(T(n, k)*T(n, 2*n-k), k=0..n-1), n=1..30); # G. C. Greubel, Nov 04 2019
MATHEMATICA
T[n_, k_]:= T[n, k]= If[k<3 || k==2*n, 1, Sum[T[n-1, k-j], {j, 3}]]; Table[Sum[T[n, k]*T[n, 2*n-k], {k, 0, n-1}], {n, 30}] (* G. C. Greubel, Nov 04 2019 *)
PROG
(Sage)
@CachedFunction
def T(n, k):
if (k<3 or k==2*n): return 1
else: return sum(T(n-1, k-j) for j in (1..3))
[sum(T(n, k)*T(n, 2*n-k) for k in (0..n-1)) for n in (1..30)] # G. C. Greubel, Nov 04 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Sean A. Irvine, Oct 22 2019
STATUS
approved