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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 134 |
| 6 | 1054 |
| 7 | 11848 |
| 8 | 188498 |
| 9 | 4229252 |
| 10 | 132827660 |
| 11 | 5831280558 |
| 12 | 357547362450 |
| 13 | 30623840955096 |
| 14 | 3671208716930842 |
| 15 | 616066177338250188 |
| 16 | 145118327950242179484 |
| 17 | 47979462271120402757058 |
| 18 | 22322388348068543767280728 |
| 19 | 14614554870662196578923073494 |
| 20 | 13488493387943242211496467931272 |
[1,1,2,6,24,134,1054,11848,188498,4229252, 132827660,5831280558,357547362450,30623840955096, 3671208716930842,616066177338250188, 145118327950242179484,47979462271120402757058, 22322388348068543767280728, 14614554870662196578923073494, 13488493387943242211496467931272] |