A005980 - OEIS

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A005980 as a simple table

n	a(n)
0	1
1	0
2	2
3	4
4	9
5	16
6	35
7	63
8	129
9	234
10	445
11	798
12	1458
13	2568
14	4561
15	7924
16	13770
17	23584
18	40301
19	68097
20	114646
21	191336
22	317893
23	524396
24	861054
25	1405130
26	2282651
27	3688254
28	5933463

[1,0,2,4,9,16,35,63,129,234,445,798,1458,2568, 4561,7924,13770,23584,40301,68097,114646,191336, 317893,524396,861054,1405130,2282651,3688254, 5933463]