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A175895 Number of lattice paths from (0,0) to (n,n) using steps S={(k,0),(0,k),(1,1)|0<k<=2} which never go above the line y=x. 3
1, 2, 9, 50, 314, 2116, 14949, 109246, 818978, 6263072, 48668366, 383182648, 3050196328, 24506969724, 198482172753, 1618700191002, 13281652367078, 109564878995724, 908171084052990, 7560049450347964, 63176859344766204 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..20.

EXAMPLE

a(2)=9 because we can reach (2,2) in the following ways:

(1,0),(1,0),(0,1),(0,1)

(1,0),(1,0),(0,2)

(2,0),(0,1),(0,1)

(2,0),(0,2)

(1,0),(1,1),(0,1)

(1,0),(0,1),(1,1)

(1,1),(1,0),(0,1)

(1,1),(0,1),(1,0)

(1,1)(1,1)

CROSSREFS

Cf. A006318

Sequence in context: A211789 A192945 A271960 * A020087 A277378 A079836

Adjacent sequences:  A175892 A175893 A175894 * A175896 A175897 A175898

KEYWORD

nonn

AUTHOR

Eric Werley, Dec 05 2010

STATUS

approved

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Last modified July 30 17:21 EDT 2021. Contains 346359 sequences. (Running on oeis4.)