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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 30 |
| 5 | 144 |
| 6 | 744 |
| 7 | 4049 |
| 8 | 22906 |
| 9 | 133537 |
| 10 | 797404 |
| 11 | 4855941 |
| 12 | 30057724 |
| 13 | 188635684 |
| 14 | 1197865288 |
| 15 | 7684428374 |
| 16 | 49735550690 |
| 17 | 324418503536 |
| 18 | 2130770610246 |
| 19 | 14080910729781 |
| 20 | 93563778237028 |
| 21 | 624781101890740 |
| 22 | 4190678175148708 |
| 23 | 28222633284905036 |
| 24 | 190770359607743460 |
[0,1,2,7,30,144,744,4049,22906,133537,797404, 4855941,30057724,188635684,1197865288,7684428374, 49735550690,324418503536,2130770610246, 14080910729781,93563778237028,624781101890740, 4190678175148708,28222633284905036, 190770359607743460] |