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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 84 |
| 5 | 965 |
| 6 | 12750 |
| 7 | 225967 |
| 8 | 5241880 |
| 9 | 139776345 |
| 10 | 4272148890 |
| 11 | 155402034491 |
| 12 | 6513558987540 |
| 13 | 304210965928597 |
| 14 | 15965624278036342 |
| 15 | 941149313037711975 |
| 16 | 61160783460181817520 |
| 17 | 4356686998946564113457 |
| 18 | 340627068039399668576946 |
| 19 | 29015657457166019702796787 |
[1,1,2,9,84,965,12750,225967,5241880,139776345, 4272148890,155402034491,6513558987540, 304210965928597,15965624278036342, 941149313037711975,61160783460181817520, 4356686998946564113457,340627068039399668576946, 29015657457166019702796787] |