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A118929 a(n) = Sum_{k=0..[n/2]} 2^(n-2*k-1)*C(n-1,2*k)*C(2*k,k)/(k+1)*a(k), with a(0)=1. 0
1, 1, 2, 5, 14, 44, 152, 569, 2270, 9524, 41576, 187432, 868144, 4117216, 19945408, 98523013, 495521686, 2534420852, 13167361256, 69417635240, 370991119792, 2008036459744, 10997771773888, 60896581502800, 340633178891872 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Invariant column vector V under matrix product A091894*V = V: a(n) = Sum_{k=0,[n/2]} A091894(n,k)*a(k), where A091894(n,k) = number of Dyck paths of semilength n, having k ddu's [here u=(1,1) and d=(1,-1)].

LINKS

Table of n, a(n) for n=0..24.

PROG

(PARI) {a(n)=if(n==0, 1, sum(k=0, n\2, 2^(n-2*k-1)*binomial(n-1, 2*k)*binomial(2*k, k)/(k+1)*a(k)))}

CROSSREFS

Cf. A091894.

Sequence in context: A119021 A002890 A202856 * A287252 A204064 A081558

Adjacent sequences:  A118926 A118927 A118928 * A118930 A118931 A118932

KEYWORD

nonn

AUTHOR

Paul D. Hanna, May 06 2006

STATUS

approved

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Last modified July 16 11:09 EDT 2020. Contains 335784 sequences. (Running on oeis4.)