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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 23 |
| 5 | 225 |
| 6 | 2824 |
| 7 | 42670 |
| 8 | 762286 |
| 9 | 15647321 |
| 10 | 363901749 |
| 11 | 9443387329 |
| 12 | 270721307582 |
| 13 | 8493470965716 |
| 14 | 289518611494068 |
| 15 | 10653599202688527 |
| 16 | 420933469388468297 |
| 17 | 17773313165985120798 |
| 18 | 798686060913371460133 |
| 19 | 38058408270727983373232 |
[1,1,0,3,23,225,2824,42670,762286,15647321, 363901749,9443387329,270721307582,8493470965716, 289518611494068,10653599202688527, 420933469388468297,17773313165985120798, 798686060913371460133,38058408270727983373232] |