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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 18 |
| 5 | 80 |
| 6 | 495 |
| 7 | 2856 |
| 8 | 20244 |
| 9 | 142848 |
| 10 | 1167885 |
| 11 | 9729280 |
| 12 | 90858438 |
| 13 | 872361984 |
| 14 | 9193900443 |
| 15 | 99947258880 |
| 16 | 1175452387560 |
| 17 | 14270843322368 |
| 18 | 185456745850329 |
| 19 | 2487099677147136 |
| 20 | 35413726451731770 |
| 21 | 519907295578030080 |
| 22 | 8052572864648861703 |
| 23 | 128451121643116822528 |
[0,0,1,3,18,80,495,2856,20244,142848,1167885, 9729280,90858438,872361984,9193900443,99947258880, 1175452387560,14270843322368,185456745850329, 2487099677147136,35413726451731770, 519907295578030080,8052572864648861703, 128451121643116822528] |