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A047002 T(n,n), array T given by A047000. 2
1, 1, 2, 7, 23, 83, 299, 1107, 4122, 15523, 58769, 223848, 856085, 3286687, 12656513, 48871469, 189145479, 733547091, 2849962925, 11090427510, 43219527353, 168645172164, 658834266936, 2576566240218, 10086236606187 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Alternatively, this sequence counts the meanders (walks starting at the origin and ending at any altitude >= 0 that may touch but never go below the x-axis) with n steps from {-2,-1,1,2}. - David Nguyen, Dec 20 2016

LINKS

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

C. Banderier, C. Krattenthaler, A. Krinik, D. Kruchinin, V. Kruchinin, D. Nguyen, and M. Wallner, Explicit formulas for enumeration of lattice paths: basketball and the kernel method, arXiv preprint arXiv:1609.06473 [math.CO], 2016.

CROSSREFS

Cf. A278398.

Sequence in context: A176287 A119371 A151290 * A127497 A151291 A150334

Adjacent sequences:  A046999 A047000 A047001 * A047003 A047004 A047005

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified March 26 23:19 EDT 2017. Contains 284141 sequences.