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A007561 as a simple table

n a(n)
0 0
1 1
2 1
3 1
4 3
5 6
6 16
7 43
8 120
9 339
10 985
11 2892
12 8606
13 25850
14 78347
15 239161
16 734922
17 2271085
18 7054235
19 22010418
20 68958139
21 216842102
22 684164551
23 2165240365
24 6871792256
25 21865189969
26 69737972975
27 222915760126
28 714001019626
29 2291298553660
30 7366035776888

[0,1,1,1,3,6,16,43,120,339,985,2892,8606,25850,
 78347,239161,734922,2271085,7054235,22010418,
 68958139,216842102,684164551,2165240365,
 6871792256,21865189969,69737972975,222915760126,
 714001019626,2291298553660,7366035776888]

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Last modified December 12 22:06 EST 2019. Contains 329963 sequences. (Running on oeis4.)