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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 38 |
| 5 | 315 |
| 6 | 3932 |
| 7 | 58828 |
| 8 | 1049108 |
| 9 | 21523445 |
| 10 | 500010024 |
| 11 | 12968712306 |
| 12 | 371504436220 |
| 13 | 11649042561247 |
| 14 | 396857394156656 |
| 15 | 14596463012746392 |
| 16 | 576460752571867208 |
| 17 | 24330595937833434249 |
| 18 | 1092955779880370116836 |
| 19 | 52063675148955620766430 |
| 20 | 2621440000000512000336088 |
[1,1,2,6,38,315,3932,58828,1049108,21523445, 500010024,12968712306,371504436220,11649042561247, 396857394156656,14596463012746392, 576460752571867208,24330595937833434249, 1092955779880370116836,52063675148955620766430, 2621440000000512000336088] |