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A002870 as a simple table

n a(n)
1 1
2 1
3 3
4 7
5 25
6 90
7 350
8 1701
9 7770
10 42525
11 246730
12 1379400
13 9321312
14 63436373
15 420693273
16 3281882604
17 25708104786
18 197462483400
19 1709751003480
20 15170932662679
21 132511015347084
22 1241963303533920
23 12320068811796900
24 120622574326072500
25 1203163392175387500

[1,1,3,7,25,90,350,1701,7770,42525,246730,1379400,
 9321312,63436373,420693273,3281882604,25708104786,
 197462483400,1709751003480,15170932662679,
 132511015347084,1241963303533920,
 12320068811796900,120622574326072500,
 1203163392175387500]

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Last modified January 20 19:53 EST 2020. Contains 331096 sequences. (Running on oeis4.)