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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 15 |
| 3 | 220 |
| 4 | 4845 |
| 5 | 142506 |
| 6 | 5245786 |
| 7 | 231917400 |
| 8 | 11969016345 |
| 9 | 706252528630 |
| 10 | 46897636623981 |
| 11 | 3461014728350400 |
| 12 | 281014969393251275 |
| 13 | 24894763097057357700 |
| 14 | 2389461906843449885700 |
| 15 | 247012484980695576597296 |
| 16 | 27361230617617949782033713 |
| 17 | 3233032526324680287912449550 |
[1,2,15,220,4845,142506,5245786,231917400, 11969016345,706252528630,46897636623981, 3461014728350400,281014969393251275, 24894763097057357700,2389461906843449885700, 247012484980695576597296, 27361230617617949782033713, 3233032526324680287912449550] |