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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 12 |
| 6 | 25 |
| 7 | 150 |
| 8 | 378 |
| 9 | 1960 |
| 10 | 8154 |
| 11 | 81540 |
| 12 | 261250 |
| 13 | 3135000 |
| 14 | 19358040 |
| 15 | 160331626 |
| 16 | 719579700 |
| 17 | 11513275200 |
| 18 | 62702704800 |
| 19 | 1128648686400 |
| 20 | 7122671957664 |
| 21 | 88475482100520 |
| 22 | 905279068633800 |
| 23 | 19916139509943600 |
[1,1,1,2,3,12,25,150,378,1960,8154,81540,261250, 3135000,19358040,160331626,719579700,11513275200, 62702704800,1128648686400,7122671957664, 88475482100520,905279068633800,19916139509943600] |