OFFSET
0,2
REFERENCES
D. Gouyou-Beauchamps, "Tableaux de Havender standards," in S. Brlek, editor, Parallélisme: Modèles et Complexité. LACIM, Université du Québec à Montréal, 1989.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
D. Gouyou-Beauchamps, Tableaux de Havender standards, Parallélisme: Modèles et Complexité. LACIM, Université du Québec à Montréal, 1989. (Annotated scanned copy)
FORMULA
G.f.: (sqrt(1-5*x^2) - sqrt(1-9*x^2)) / (2 * x^2 * sqrt(1-x^2)) [from Gouyou-Beauchamps]. - Sean A. Irvine, Dec 28 2017
a(n) = Sum_{q=0..2*n} Sum_{j=max(0, n-q)..floor((2*n-q)/2)} n! * (4*n-2*q-2*j)! / ((2*n-q-2*j)! * (j+1)! * ((2*n-q-j)!)^2 * (q-n+j)!) [from Gouyou-Beauchamps]. - Sean A. Irvine, Dec 28 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Sean A. Irvine, Dec 28 2017
STATUS
approved