References to A000139

a(n) = 2*(3*n)!/((2*n+1)!*((n+1)!)).
2, 1, 2, 6, 22, 91, 408, 1938, 9614, 49335, 260130, 1402440, 7702632, 42975796

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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