1,2

a(n) is 2*the sum of the areas under all Dyck paths of length n.

T. D. Noe, Table of n, a(n) for n=1..400

C. Banderier, Analytic combinatorics of random walks and planar maps, PhD Thesis, 2001.

(8*x^2+4*x-1-sqrt(1-4*x^2)*(4*x^2+4*x-1))/(4*(1-2*x)^2*(1+2*x)*x^2)

Sequence in context: A073362 A095264 A027044 this_sequence A125069 A080926 A041673

Adjacent sequences: A057568 A057569 A057570 this_sequence A057572 A057573 A057574

easy,nonn,nice

Cyril Banderier (Cyril.Banderier(AT)inria.fr), Oct 04 2000