OFFSET
1,2
LINKS
M. Bousquet-Mélou and G. Schaeffer, Enumeration of planar constellations, Adv. in Appl. Math. v.24 (2000), 337-368.
FORMULA
a(n) = 5*4^(n-1)*binomial(4*n, n)/((3*n+1)*(3*n+2)). - corrected by Michel Marcus, Dec 11 2014
D-finite with recurrence 3*n*(3*n+2)*(3*n+1)*a(n) -32*(4*n-3)*(2*n-1)*(4*n-1)*a(n-1)=0. - R. J. Mathar, Mar 29 2023
MAPLE
A090374 := proc(n)
5*4^(n-1)*binomial(4*n, n)/((3*n+1)*(3*n+2))
end proc:
seq(A090374(n), n=1..40) ; # R. J. Mathar, Mar 29 2023
MATHEMATICA
a[n_] := 5 2^(2n) (4n-1)! / ((n-1)! (3n+2)!);
Array[a, 18] (* Jean-François Alcover, Aug 28 2019 *)
PROG
(PARI) vector(20, n, 5*4^(n-1)*binomial(4*n, n)/((3*n+1)*(3*n+2))) \\ Michel Marcus, Dec 11 2014
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Valery A. Liskovets, Dec 01 2003
EXTENSIONS
More terms from Michel Marcus, Dec 11 2014
STATUS
approved