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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 35 |
| 4 | 168 |
| 5 | 766 |
| 6 | 3402 |
| 7 | 14827 |
| 8 | 63680 |
| 9 | 270313 |
| 10 | 1136546 |
| 11 | 4740986 |
| 12 | 19644984 |
| 13 | 80939021 |
| 14 | 331835984 |
| 15 | 1354628539 |
| 16 | 5508982340 |
| 17 | 22328647462 |
| 18 | 90229615030 |
| 19 | 363633214831 |
| 20 | 1461903606752 |
| 21 | 5864244756909 |
| 22 | 23476219277174 |
| 23 | 93808204087890 |
[2,6,35,168,766,3402,14827,63680,270313,1136546, 4740986,19644984,80939021,331835984,1354628539, 5508982340,22328647462,90229615030,363633214831, 1461903606752,5864244756909,23476219277174, 93808204087890] |