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A081621 as a simple table

n a(n)
4 0
5 0
6 0
7 0
8 0
9 0
10 0
11 0
12 1
13 0
14 1
15 1
16 3
17 4
18 12
19 23
20 73
21 192
22 651
23 2070
24 7290
25 25381
26 91441
27 329824
28 1204737
29 4412031
30 16248772
31 59995535
32 222231424
33 825028656
34 3069993552
35 11446245342
36 42758608761
37 160012226334
38 599822851579
39 2252137171764
40 8469193859271
41 31896058068930

[0,0,0,0,0,0,0,0,1,0,1,1,3,4,12,23,73,192,651,
 2070,7290,25381,91441,329824,1204737,4412031,
 16248772,59995535,222231424,825028656,3069993552,
 11446245342,42758608761,160012226334,599822851579,
 2252137171764,8469193859271,31896058068930]

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Last modified April 24 13:24 EDT 2024. Contains 371955 sequences. (Running on oeis4.)