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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 25 |
| 5 | 130 |
| 6 | 700 |
| 7 | 3876 |
| 8 | 21945 |
| 9 | 126500 |
| 10 | 740025 |
| 11 | 4382625 |
| 12 | 26225628 |
| 13 | 158331880 |
| 14 | 963250600 |
| 15 | 5899491640 |
| 16 | 36345082425 |
| 17 | 225082957512 |
| 18 | 1400431689475 |
| 19 | 8749779798375 |
| 20 | 54874635255825 |
| 21 | 345329274848250 |
| 22 | 2179969531405680 |
[1,0,1,5,25,130,700,3876,21945,126500,740025, 4382625,26225628,158331880,963250600,5899491640, 36345082425,225082957512,1400431689475, 8749779798375,54874635255825,345329274848250, 2179969531405680] |