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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 33 |
| 4 | 276 |
| 5 | 4150 |
| 6 | 65300 |
| 7 | 1083425 |
| 8 | 20965000 |
| 9 | 399876876 |
| 10 | 8461219032 |
| 11 | 178642861782 |
| 12 | 4010820554664 |
| 13 | 90684123972156 |
| 14 | 2130950905378152 |
| 15 | 50560833176021025 |
| 16 | 1231721051614138800 |
| 17 | 30294218438009039800 |
| 18 | 759645100717216142000 |
| 19 | 19213764100954274616908 |
| 20 | 493269287121905287769776 |
[1,1,2,33,276,4150,65300,1083425,20965000, 399876876,8461219032,178642861782,4010820554664, 90684123972156,2130950905378152,50560833176021025, 1231721051614138800,30294218438009039800, 759645100717216142000,19213764100954274616908, 493269287121905287769776] |