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A029760 A sum with next-to-central binomial coefficients of even order, Catalan related. 8
1, 8, 47, 244, 1186, 5536, 25147, 112028, 491870, 2135440, 9188406, 39249768, 166656772, 704069248, 2961699667, 12412521388, 51854046982, 216013684528, 897632738722, 3721813363288, 15401045060572, 63616796642368, 262357557683422, 1080387930269464 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Proof by induction.

a(n) = total area below paths consisting of steps east (1,0) and north (0,1) from (0,0) to (n+2,n+2) that stay weakly below y=x. For example, the two paths with n=0 are

. _|.....|

_|.....__|

The first has area 1 below it, the second area 0 and so a(0)=1. - David Callan, Dec 09 2004

Convolution of A000346 with A001700. - Philippe Deléham, May 19 2009

LINKS

Table of n, a(n) for n=0..23.

Ran Pan, Jeffrey B. Remmel, Paired patterns in lattice paths, arXiv:1601.07988 [math.CO], 2016.

FORMULA

a(n) = 4^(n+1)*Sum_{k=1..n+1} binomial(2k, k-1)/4^k = ((n+3)^2)*C(n+2)/2-2^(2*n+3), C = Catalan. Also a(n+1)=4*a(n)+binomial(2(n+2), n+1).

G.f.: (d/dx)c(x)/(1-4*x), where c(x) = g.f. for Catalan numbers; convolution of A001791 and powers of 4. G.f. also c(x)^2/(1-4*x)^(3/2); convolution of Catalan numbers A000108 C(n), n >= 1, with A002457; convolution of A008549(n), n >= 1, with A000984 (central binomial coefficients).

a(n) = Sum_{k=0..n+1} A039598(n+1,k)*k^2. - Philippe Deléham, Dec 16 2007

CROSSREFS

Cf. A000108, A002457, A008549, A000984, A139262.

Sequence in context: A099110 A106393 A300167 * A139262 A026900 A016198

Adjacent sequences:  A029757 A029758 A029759 * A029761 A029762 A029763

KEYWORD

nonn

AUTHOR

Wolfdieter Lang

STATUS

approved

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Last modified August 16 16:40 EDT 2018. Contains 313809 sequences. (Running on oeis4.)