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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 16 |
| 5 | 77 |
| 6 | 630 |
| 7 | 7956 |
| 8 | 132480 |
| 9 | 2664389 |
| 10 | 62140078 |
| 11 | 1643056625 |
| 12 | 48503833280 |
| 13 | 1580192424580 |
| 14 | 56292381309608 |
| 15 | 2176251789724500 |
| 16 | 90726545080501440 |
| 17 | 4056755120695005717 |
| 18 | 193649641793538259950 |
| 19 | 9828338731644277922679 |
| 20 | 528459404673048692682384 |
[1,1,2,5,16,77,630,7956,132480,2664389,62140078, 1643056625,48503833280,1580192424580, 56292381309608,2176251789724500,90726545080501440, 4056755120695005717,193649641793538259950, 9828338731644277922679,528459404673048692682384] |