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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 70 |
| 5 | 630 |
| 6 | 6930 |
| 7 | 90090 |
| 8 | 1351350 |
| 9 | 22972950 |
| 10 | 436486050 |
| 11 | 9166207050 |
| 12 | 210822762150 |
| 13 | 5270569053750 |
| 14 | 142305364451250 |
| 15 | 4126855569086250 |
| 16 | 127932522641673750 |
| 17 | 4221773247175233750 |
| 18 | 147762063651133181250 |
| 19 | 5467196355091927706250 |
| 20 | 213220657848585180543750 |
[1,1,2,10,70,630,6930,90090,1351350,22972950, 436486050,9166207050,210822762150,5270569053750, 142305364451250,4126855569086250, 127932522641673750,4221773247175233750, 147762063651133181250,5467196355091927706250, 213220657848585180543750] |