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
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).
Crossrefs
Column k=4 of A291883.
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)).