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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 62 |
| 5 | 630 |
| 6 | 8342 |
| 7 | 135366 |
| 8 | 2515550 |
| 9 | 54183030 |
| 10 | 1310234822 |
| 11 | 35319829446 |
| 12 | 1049464490318 |
| 13 | 34071885335670 |
| 14 | 1200517165372982 |
| 15 | 45618622297335366 |
| 16 | 1859845702950209726 |
| 17 | 80979474394316143350 |
| 18 | 3750512276232725996582 |
| 19 | 184110786990184360818246 |
[1,0,2,6,62,630,8342,135366,2515550,54183030, 1310234822,35319829446,1049464490318, 34071885335670,1200517165372982,45618622297335366, 1859845702950209726,80979474394316143350, 3750512276232725996582,184110786990184360818246] |