OFFSET
6,2
COMMENTS
Number of standard tableaux of shape (n-5,2,2,2,2) (n>=7). - Emeric Deutsch, May 20 2004
Number of short bushes with n+3 edges and 5 branch nodes (i.e. nodes with outdegree at least 2; a short bush is an ordered tree with no nodes of outdegree 1). Example: a(7)=42 because the only short bushes with 10 edges and 5 branch nodes are the fortytwo full binary trees with 10 edges. Column 5 of A108263. - Emeric Deutsch, May 29 2005
LINKS
D. Beckwith, Legendre polynomials and polygon dissections?, Amer. Math. Monthly, 105 (1998), 256-257.
F. R. Bernhart, Catalan, Motzkin and Riordan numbers, Discr. Math., 204 (1999), 73-112.
FORMULA
a(n) = binomial(n+3, 4)*binomial(n-3, 4)/5.
G.f.: z^7(42-48z+27z^2-8z^3+z^4)/(1-z)^9. - Emeric Deutsch, May 29 2005
PROG
(PARI) vector(40, n, n+=5; binomial(n+3, 4)*binomial(n-3, 4)/5) \\ Michel Marcus, Jun 18 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved