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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 92 |
| 5 | 510 |
| 6 | 7074 |
| 7 | 68040 |
| 8 | 1002224 |
| 9 | 12529944 |
| 10 | 228706920 |
| 11 | 3565888920 |
| 12 | 71035245192 |
| 13 | 1348127454960 |
| 14 | 30270949077264 |
| 15 | 661700017709640 |
| 16 | 16516072112482560 |
| 17 | 408336559236083520 |
| 18 | 11204399270843020224 |
| 19 | 309489391954850336640 |
| 20 | 9258803420755891835520 |
[1,0,2,9,92,510,7074,68040,1002224,12529944, 228706920,3565888920,71035245192,1348127454960, 30270949077264,661700017709640,16516072112482560, 408336559236083520,11204399270843020224, 309489391954850336640,9258803420755891835520] |