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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 1 |
| 8 | 2 |
| 9 | 18 |
| 10 | 162 |
| 11 | 1122 |
| 12 | 6402 |
| 13 | 31746 |
| 14 | 141570 |
| 15 | 580866 |
| 16 | 2241096 |
| 17 | 8693256 |
| 18 | 43232904 |
| 19 | 362491272 |
| 20 | 4067218584 |
| 21 | 45304757784 |
| 22 | 459941563224 |
| 23 | 4236342378840 |
| 24 | 35804034476496 |
| 25 | 281634733757520 |
| 26 | 2106753678778320 |
| 27 | 15739783039815120 |
[1,1,1,1,1,1,1,1,2,18,162,1122,6402,31746,141570, 580866,2241096,8693256,43232904,362491272, 4067218584,45304757784,459941563224,4236342378840, 35804034476496,281634733757520,2106753678778320, 15739783039815120] |