A291888 Number of symmetrically unique Dyck paths of semilength n and height four.

1, 4, 19, 69, 252, 855, 2867, 9339, 30085, 95524, 300796, 939228, 2915481, 9001380, 27675779, 84782673, 258956584, 788926699, 2398385803, 7277878707, 22050326805, 66718218120, 201640080056, 608808949752, 1836608777233, 5536482441124, 16679237438035

Offset

4,2

Links

Alois P. Heinz, Table of n, a(n) for n = 4..1000

Index entries for linear recurrences with constant coefficients, signature (8, -19, -2, 66, -76, 3, 30, -9).

Formula

G.f.: x^4*(3*x^4-5*x^3+6*x^2-4*x+1)/((x-1)*(3*x-1)*(x^2-3*x+1)*(3*x^2-1)*(x^2+x-1)).

Crossrefs

Column k=4 of A291883.

Sequence in context: A000306 A100185 A357251 * A217324 A129019 A167247

Adjacent sequences: A291885 A291886 A291887 * A291889 A291890 A291891

Keyword

nonn,easy

Author

Alois P. Heinz, Sep 05 2017

Status

approved