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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 10 |
| 4 | 63 |
| 5 | 336 |
| 6 | 1650 |
| 7 | 7722 |
| 8 | 35035 |
| 9 | 155584 |
| 10 | 680238 |
| 11 | 2939300 |
| 12 | 12584726 |
| 13 | 53488800 |
| 14 | 225990180 |
| 15 | 950094810 |
| 16 | 3977737875 |
| 17 | 16594533120 |
| 18 | 69018792150 |
| 19 | 286296636780 |
| 20 | 1184823735810 |
| 21 | 4893253404000 |
| 22 | 20171905282620 |
| 23 | 83020426503300 |
[0,1,10,63,336,1650,7722,35035,155584,680238, 2939300,12584726,53488800,225990180,950094810, 3977737875,16594533120,69018792150,286296636780, 1184823735810,4893253404000,20171905282620, 83020426503300] |