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 A161581 (3n)!/(n!(n+1)!(n+2)!) 3

%I

%S 21,231,3003,43758,692835,11685817,207157665,3823000545,72931087320,

%T 1430571328200,28734046963560,589047962752980,12292044987448215,

%U 260543149635912165,5599392250947235125,121830987186399315825

%N (3n)!/(n!(n+1)!(n+2)!)

%C 3-d analog of the Catalan numbers A000108.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/BinomialSums.html"> Binomial Sums</a>.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CentralBinomialCoefficient.html"> Central Binomial Coefficient</a>.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/CatalanNumber.html"> Catalan Number</a>.

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

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

%p 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]

%Y Cf. A000108, A006480.

%K nonn

%O 3,1

%A _Alexander Adamchuk_, Jun 14 2009

%E Removed repetitions of information contained in other sequences - _R. J. Mathar_, Jun 16 2009

%E More terms from _Emeric Deutsch_, Jun 14 2009

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Last modified January 19 09:35 EST 2019. Contains 319306 sequences. (Running on oeis4.)