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(3n)!/[3n*n!*(n+1)!]
2

%I #9 Mar 30 2012 18:58:11

%S 1,10,280,13860,1009008,98017920,11972188800,1766895530400,

%T 306261891936000,61040779261862400,13761921142674432000,

%U 3464298995338621440000,963455812901426718720000,293441113300834537758720000

%N (3n)!/[3n*n!*(n+1)!]

%t Table[(3n)!/(3n*n!*(n+1)!),{n,1,14}]

%K nonn

%O 1,2

%A _Clark Kimberling_, Feb 01 2012