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A001447 as a simple table

na(n)
01
13
215
365
4325
51575
67875
739125
8195625
9976875
104884375
1124415625
12122078125
13610359375
143051796875
1515258828125
1676294140625
17381469921875
181907349609375
199536744140625
2047683720703125

[1,3,15,65,325,1575,7875,39125,195625,976875,
 4884375,24415625,122078125,610359375,3051796875,
 15258828125,76294140625,381469921875,
 1907349609375,9536744140625,47683720703125]