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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 31 |
| 4 | 364 |
| 5 | 5746 |
| 6 | 113944 |
| 7 | 2719291 |
| 8 | 75843724 |
| 9 | 2420160286 |
| 10 | 86941080904 |
| 11 | 3471911602006 |
| 12 | 152562875644984 |
| 13 | 7315129181611876 |
| 14 | 380045172886143664 |
| 15 | 21266347877729314771 |
| 16 | 1275148311699896290444 |
| 17 | 81563275661324271278566 |
[1,1,4,31,364,5746,113944,2719291,75843724, 2420160286,86941080904,3471911602006, 152562875644984,7315129181611876, 380045172886143664,21266347877729314771, 1275148311699896290444,81563275661324271278566] |