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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 160 |
| 5 | 1830 |
| 6 | 25074 |
| 7 | 395248 |
| 8 | 6990876 |
| 9 | 136464705 |
| 10 | 2906040280 |
| 11 | 66938704602 |
| 12 | 1656963703434 |
| 13 | 43848218457953 |
| 14 | 1235194571623950 |
| 15 | 36905133359883240 |
| 16 | 1165832901366137184 |
| 17 | 38830278855693956931 |
| 18 | 1360186936717777641747 |
| 19 | 49995325008141402758320 |
[1,1,3,18,160,1830,25074,395248,6990876,136464705, 2906040280,66938704602,1656963703434, 43848218457953,1235194571623950,36905133359883240, 1165832901366137184,38830278855693956931, 1360186936717777641747,49995325008141402758320] |