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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 15 |
| 4 | 284 |
| 5 | 8575 |
| 6 | 345460 |
| 7 | 17190684 |
| 8 | 1012901520 |
| 9 | 68810750943 |
| 10 | 5291667341342 |
| 11 | 454479660308531 |
| 12 | 43140290728900554 |
| 13 | 4487833959824527910 |
| 14 | 508072065566891421336 |
| 15 | 62222074620010689986918 |
| 16 | 8200304581300850453687880 |
| 17 | 1157674985567876068399895997 |
| 18 | 174357014524193551292388873190 |
[1,1,2,15,284,8575,345460,17190684,1012901520, 68810750943,5291667341342,454479660308531, 43140290728900554,4487833959824527910, 508072065566891421336,62222074620010689986918, 8200304581300850453687880, 1157674985567876068399895997, 174357014524193551292388873190] |