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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 38 |
| 5 | 326 |
| 6 | 3739 |
| 7 | 53808 |
| 8 | 927420 |
| 9 | 18578248 |
| 10 | 423649565 |
| 11 | 10828720882 |
| 12 | 306545462810 |
| 13 | 9518362652994 |
| 14 | 321605286435431 |
| 15 | 11745699035775884 |
| 16 | 461063683165975712 |
| 17 | 19357125741005727156 |
| 18 | 865493449685182242777 |
[0,1,6,38,326,3739,53808,927420,18578248, 423649565,10828720882,306545462810,9518362652994, 321605286435431,11745699035775884, 461063683165975712,19357125741005727156, 865493449685182242777] |