OFFSET
0,2
FORMULA
a(n) = A074911(2*n,n).
MAPLE
b:= proc(x, y) option remember; `if`(x=0, y!,
b(x-1, y)+b(sort([x, y-1])[]))
end:
a:= n-> b(n$2):
seq(a(n), n=0..26); # Alois P. Heinz, Jul 14 2021
MATHEMATICA
T[n_, 0] := n!; T[n_, n_] := n!;
T[n_, k_] /; 0<k<n := T[n, k] = T[n-1, k-1]+T[n-1, k];
a[n_] := T[2n, n];
Table[a[n], {n, 0, 21}] (* Jean-François Alcover, Nov 03 2022 *)
PROG
(Haskell)
a227791 n = a227550 (2 * n) n
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Aug 05 2013
STATUS
approved