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A161581 (3n)!/(n!(n+1)!(n+2)!) 3
21, 231, 3003, 43758, 692835, 11685817, 207157665, 3823000545, 72931087320, 1430571328200, 28734046963560, 589047962752980, 12292044987448215, 260543149635912165, 5599392250947235125, 121830987186399315825 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

3-d analog of the Catalan numbers A000108.

LINKS

Table of n, a(n) for n=3..18.

Eric Weisstein's World of Mathematics, Binomial Sums.

Eric Weisstein's World of Mathematics, Central Binomial Coefficient.

Eric Weisstein's World of Mathematics, Catalan Number.

FORMULA

a(n) = A006480(n)/((n+1)^2*(n+2)).

MAPLE

A161581 := proc(n) (3*n)!/n!/(n+1)!/(n+2)! ; end: seq(A161581(n), n=3..40) ; # R. J. Mathar, Jun 16 2009

a := proc (n) options operator, arrow: factorial(3*n)/(factorial(n)*factorial(n+1)*factorial(n+2)) end proc: seq(a(n), n = 3 .. 20); [From Emeric Deutsch, Jun 14 2009]

CROSSREFS

Cf. A000108, A006480.

Sequence in context: A010973 A022586 A125409 * A069601 A173347 A089937

Adjacent sequences:  A161578 A161579 A161580 * A161582 A161583 A161584

KEYWORD

nonn

AUTHOR

Alexander Adamchuk, Jun 14 2009

EXTENSIONS

Removed repetitions of information contained in other sequences - R. J. Mathar, Jun 16 2009

More terms from Emeric Deutsch, Jun 14 2009

STATUS

approved

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Last modified May 27 22:57 EDT 2017. Contains 287210 sequences.