OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..36
J. Fürlinger, J. Hofbauer, q-Catalan numbers, Journal of Combinatorial Theory, Series A, Volume 40, Issue 2, November 1985, Pages 248-264.
Robin Sulzgruber, The Symmetry of the q,t-Catalan Numbers, Masterarbeit, University of Vienna. Fakultät für Mathematik, 2013.
FORMULA
a(n) = [x^n] 1/(1-x/(1-n*x/(1-n^2*x/(1-n^3*x/(1-n^4*x/(1- ... )))))).
a(n) ~ n^(n*(n-1)/2). - Vaclav Kotesovec, Aug 19 2017
MAPLE
b:= proc(n, k) option remember; `if`(n=0, 1, add(
b(j, k)*b(n-j-1, k)*k^j, j=0..n-1))
end:
a:= n-> b(n$2):
seq(a(n), n=0..12);
MATHEMATICA
b[n_, k_]:=b[n, k]=If[n==0, 1, Sum[b[j, k] b[n - j - 1, k]*k^j, {j, 0, n - 1}]]; Table[b[n, n], {n, 0, 15}] (* Indranil Ghosh, Aug 10 2017 *)
PROG
(Python)
from sympy.core.cache import cacheit
@cacheit
def b(n, k):
if n == 0:
return 1
return sum(b(j, k) * b(n - j - 1, k) * k**j for j in range(n))
def a(n): return b(n, n)
print([a(n) for n in range(16)]) # Indranil Ghosh, Aug 10 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 10 2017
STATUS
approved