OFFSET
1,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..50
N. J. A. Sloane, Transforms
MAPLE
a:= proc(n) option remember; `if`(n<0, 0,
`if`(n=0, 1, binomial(2*n, n)/(n+1) *a(n-1) +a(n-2)))
end:
seq(a(n), n=1..20); # Alois P. Heinz, Aug 06 2013
MATHEMATICA
a[n_] := a[n] = If[n<0, 0, If[n==0, 1, CatalanNumber[n]*a[n-1] + a[n-2]]]; Table[a[n], {n, 1, 20}] (* Jean-François Alcover, Feb 25 2017, translated from Maple *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 10 2002
STATUS
approved