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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 21 |
| 4 | 182 |
| 5 | 2093 |
| 6 | 23394 |
| 7 | 285383 |
| 8 | 3621150 |
| 9 | 47813367 |
| 10 | 650302814 |
| 11 | 9066061193 |
| 12 | 128986881660 |
| 13 | 1866877313441 |
| 14 | 27417577343674 |
| 15 | 407771633368995 |
| 16 | 6131640430397790 |
| 17 | 93096368350684720 |
| 18 | 1425633583562073228 |
| 19 | 21998953427963954547 |
| 20 | 341803226976420690600 |
[1,1,0,21,182,2093,23394,285383,3621150,47813367, 650302814,9066061193,128986881660,1866877313441, 27417577343674,407771633368995,6131640430397790, 93096368350684720,1425633583562073228, 21998953427963954547,341803226976420690600] |