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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 44 |
| 6 | 265 |
| 7 | 1854 |
| 8 | 14833 |
| 9 | 133496 |
| 10 | 1053136 |
| 11 | 7429428 |
| 12 | 48212485 |
| 13 | 296810944 |
| 14 | 1780911209 |
| 15 | 10628061638 |
| 16 | 63975026748 |
| 17 | 392088233154 |
| 18 | 2461796588937 |
| 19 | 15675639817952 |
| 20 | 100493852548697 |
| 21 | 645295580260184 |
| 22 | 4136342103328781 |
| 23 | 26418529357842470 |
| 24 | 168032289856555025 |
[1,0,1,2,9,44,265,1854,14833,133496,1053136, 7429428,48212485,296810944,1780911209,10628061638, 63975026748,392088233154,2461796588937, 15675639817952,100493852548697,645295580260184, 4136342103328781,26418529357842470, 168032289856555025] |