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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 104 |
| 6 | 531 |
| 7 | 2982 |
| 8 | 18109 |
| 9 | 117545 |
| 10 | 808764 |
| 11 | 5862253 |
| 12 | 44553224 |
| 13 | 353713232 |
| 14 | 2924697019 |
| 15 | 25124481690 |
| 16 | 223768976093 |
| 17 | 2062614190733 |
| 18 | 19646231085928 |
| 19 | 193102738376890 |
| 20 | 1956191484175505 |
| 21 | 20401540100814142 |
| 22 | 218825717967033373 |
| 23 | 2411606083999341827 |
[1,1,2,6,23,104,531,2982,18109,117545,808764, 5862253,44553224,353713232,2924697019,25124481690, 223768976093,2062614190733,19646231085928, 193102738376890,1956191484175505, 20401540100814142,218825717967033373, 2411606083999341827] |