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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 23 |
| 6 | 136 |
| 7 | 872 |
| 8 | 6952 |
| 9 | 62813 |
| 10 | 641536 |
| 11 | 7277342 |
| 12 | 90825472 |
| 13 | 1236592403 |
| 14 | 18239374336 |
| 15 | 289719603812 |
| 16 | 4930706056192 |
| 17 | 89509486108793 |
| 18 | 1726465695809536 |
| 19 | 35259035421020282 |
| 20 | 760088211047514112 |
| 21 | 17247810060070731983 |
| 22 | 410954011551070683136 |
| 23 | 10257838886120978286752 |
[1,1,1,2,7,23,136,872,6952,62813,641536,7277342, 90825472,1236592403,18239374336,289719603812, 4930706056192,89509486108793,1726465695809536, 35259035421020282,760088211047514112, 17247810060070731983,410954011551070683136, 10257838886120978286752] |