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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 12 |
| 5 | 35 |
| 6 | 144 |
| 7 | 910 |
| 8 | 5976 |
| 9 | 39942 |
| 10 | 306570 |
| 11 | 2698223 |
| 12 | 25536132 |
| 13 | 257563618 |
| 14 | 2813856192 |
| 15 | 33154390275 |
| 16 | 415692891552 |
| 17 | 5523237345701 |
| 18 | 77778820305558 |
| 19 | 1157352664763569 |
| 20 | 18120617730892800 |
| 21 | 297774609082108662 |
| 22 | 5127157782095091402 |
| 23 | 92308888110570124310 |
[1,1,0,3,12,35,144,910,5976,39942,306570,2698223, 25536132,257563618,2813856192,33154390275, 415692891552,5523237345701,77778820305558, 1157352664763569,18120617730892800, 297774609082108662,5127157782095091402, 92308888110570124310] |