A208976 Row sums of the triangle in A208101.

1, 2, 4, 8, 15, 29, 54, 104, 195, 377, 713, 1385, 2639, 5147, 9866, 19304, 37179, 72929, 140997, 277133, 537471, 1058147, 2057509, 4056233, 7904455, 15600899, 30458899, 60174899, 117675359, 232676279, 455657714, 901620584, 1767883499, 3500409329, 6871173869

Offset

0,2

Comments

a(n) = A050168(n+1) - 1.

Number of Dyck (n+1)-paths that are symmetric after deleting all leading hills. - David Scambler, Aug 23 2012

Links

Reinhard Zumkeller, Table of n, a(n) for n = 0..1000

Formula

a(n) = A001405(n) + A001405(n+1) - 1.

Mathematica

T[_, 0] = 1; T[n_, 1] := n; T[n_, n_] := T[n - 1, n - 2]; T[n_, k_] /; 1 < k < n := T[n, k] = T[n - 1, k] + T[n - 1, k - 2];
a[n_] := Sum[T[n, k], {k, 0, n}];
Table[a[n], {n, 0, 40}] (* Jean-François Alcover, Feb 03 2018, from A208101 *)

Prog

(Haskell)
a208976 n = a208976_list !! n
a208976_list = map (subtract 1) $ tail a050168_list

Crossrefs

Sequence in context: A036621 A001383 A217733 * A278554 A335473 A374697

Adjacent sequences: A208973 A208974 A208975 * A208977 A208978 A208979

Keyword

nonn

Author

Reinhard Zumkeller, Mar 04 2012

Status

approved