a(n) = (2*n)!/(n+1)!.
1, 1, 4, 30, 336, 5040, 95040, 2162160, 57657600, 1764322560, 60949324800
3 seqfan posts
Thu Feb 23 16:42:45 CET 2012 [seqfan] Re: Question on A001761
Wed Feb 22 22:26:29 CET 2012 [seqfan] Re: Question on A001761
Wed Feb 22 18:19:58 CET 2012 [seqfan] Question on A001761
Index of A-numbers in seqfan: by ascending order
by month
by frequency
by keyword
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