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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 74 |
| 5 | 1400 |
| 6 | 35676 |
| 7 | 1140328 |
| 8 | 43740848 |
| 9 | 1954336608 |
| 10 | 99561874080 |
| 11 | 5691393582336 |
| 12 | 360561583177440 |
| 13 | 25064797000415744 |
| 14 | 1896477768217789120 |
| 15 | 155128714525468598400 |
| 16 | 13639839907494680219648 |
| 17 | 1282811359778733608826368 |
| 18 | 128498290985443181787800064 |
| 19 | 13657938489514600713859515392 |
| 20 | 1535272989503239280608301470720 |
| 21 | 181975961346350933380240113192960 |
[1,1,6,74,1400,35676,1140328,43740848,1954336608, 99561874080,5691393582336,360561583177440, 25064797000415744,1896477768217789120, 155128714525468598400,13639839907494680219648, 1282811359778733608826368, 128498290985443181787800064, 13657938489514600713859515392, 1535272989503239280608301470720, 181975961346350933380240113192960] |