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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 42 |
| 3 | 786 |
| 4 | 17736 |
| 5 | 459768 |
| 6 | 13333488 |
| 7 | 425600976 |
| 8 | 14791250688 |
| 9 | 555381292800 |
| 10 | 22398626084352 |
| 11 | 965768866650624 |
| 12 | 44347055502428160 |
| 13 | 2161455366606034944 |
| 14 | 111489317304231616512 |
| 15 | 6069676735484389779456 |
| 16 | 347921629212782938472448 |
| 17 | 20950823605616500202323968 |
| 18 | 1322561808699778749456678912 |
[1,3,42,786,17736,459768,13333488,425600976, 14791250688,555381292800,22398626084352, 965768866650624,44347055502428160, 2161455366606034944,111489317304231616512, 6069676735484389779456,347921629212782938472448, 20950823605616500202323968, 1322561808699778749456678912] |