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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 16 |
| 4 | 175 |
| 5 | 1771 |
| 6 | 17906 |
| 7 | 184920 |
| 8 | 1958979 |
| 9 | 21253375 |
| 10 | 235401166 |
| 11 | 2653427140 |
| 12 | 30356604642 |
| 13 | 351714783980 |
| 14 | 4119532070980 |
| 15 | 48708027030608 |
| 16 | 580682498991627 |
| 17 | 6973355148949335 |
| 18 | 84286653134676230 |
| 19 | 1024694093358751200 |
| 20 | 12522664845237058050 |
| 21 | 153762682169941498170 |
[1,16,175,1771,17906,184920,1958979,21253375, 235401166,2653427140,30356604642,351714783980, 4119532070980,48708027030608,580682498991627, 6973355148949335,84286653134676230, 1024694093358751200,12522664845237058050, 153762682169941498170] |