References to A000168

2*3^n*(2*n)!/(n!*(n+2)!).
1, 2, 9, 54, 378, 2916, 24057, 208494, 1876446, 17399772, 165297834, 1602117468


1 seqfan posts

Fri Oct 29 05:35:16 CEST 2010    [seqfan] Implementing first 500 sequences in Java

Index of A-numbers in seqfan: by ascending order    by month    by frequency    by keyword
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