A227791 Central terms of the triangle in A227550.

1, 2, 8, 36, 176, 940, 5568, 37128, 280992, 2410812, 23250080, 249164344, 2934303264, 37617633976, 521009920256, 7748175156240, 123095897716800, 2080205257723740, 37253560076385120, 704703668205036120, 14039778681732928800, 293831851498842784680

Offset

0,2

Links

Table of n, a(n) for n=0..21.

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

Cf. A074911, A225621, A227550.

Sequence in context: A166229 A109318 A113327 * A245102 A129148 A285672

Adjacent sequences: A227788 A227789 A227790 * A227792 A227793 A227794

Keyword

nonn

Author

Reinhard Zumkeller, Aug 05 2013

Status

approved