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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 103 |
| 6 | 512 |
| 7 | 2739 |
| 8 | 15464 |
| 9 | 90964 |
| 10 | 552570 |
| 11 | 3444473 |
| 12 | 21930271 |
| 13 | 142105583 |
| 14 | 934612523 |
| 15 | 6225356918 |
| 16 | 41923198109 |
| 17 | 285028459807 |
| 18 | 1954160675724 |
| 19 | 13497387857456 |
| 20 | 93843199637004 |
| 21 | 656325719024695 |
| 22 | 4614695142311098 |
| 23 | 32602630763193546 |
| 24 | 231343227544240096 |
[1,1,2,6,23,103,512,2739,15464,90964,552570, 3444473,21930271,142105583,934612523,6225356918, 41923198109,285028459807,1954160675724, 13497387857456,93843199637004,656325719024695, 4614695142311098,32602630763193546, 231343227544240096] |