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| n | a(n) |
|---|---|
| 3 | 2 |
| 4 | 6 |
| 5 | 21 |
| 6 | 115 |
| 7 | 865 |
| 8 | 11180 |
| 9 | 261434 |
| 10 | 11719198 |
| 11 | 1006730374 |
| 12 | 164060444228 |
| 13 | 50335933202664 |
| 14 | 29003489553692808 |
| 15 | 31397381477206877920 |
| 16 | 63969560214904127718624 |
| 17 | 245871831740396590978751568 |
| 18 | 1787331725311868949057440884912 |
| 19 | 24636021429527995774854054487417072 |
| 20 | 645465483199214927570182087868056845600 |
[2,6,21,115,865,11180,261434,11719198,1006730374, 164060444228,50335933202664,29003489553692808, 31397381477206877920,63969560214904127718624, 245871831740396590978751568, 1787331725311868949057440884912, 24636021429527995774854054487417072, 645465483199214927570182087868056845600] |