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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 150 |
| 5 | 1330 |
| 6 | 14180 |
| 7 | 176295 |
| 8 | 2505230 |
| 9 | 40049226 |
| 10 | 711379872 |
| 11 | 13899553206 |
| 12 | 296270826852 |
| 13 | 6841305568812 |
| 14 | 170127212242416 |
| 15 | 4532854743105975 |
| 16 | 128824523061126750 |
| 17 | 3890041395675793930 |
| 18 | 124375112406132404960 |
| 19 | 4197530354920789582410 |
| 20 | 149118181703716510545260 |
[1,1,4,21,150,1330,14180,176295,2505230,40049226, 711379872,13899553206,296270826852,6841305568812, 170127212242416,4532854743105975, 128824523061126750,3890041395675793930, 124375112406132404960,4197530354920789582410, 149118181703716510545260] |