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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 30 |
| 4 | 182 |
| 5 | 1224 |
| 6 | 8778 |
| 7 | 65780 |
| 8 | 508950 |
| 9 | 4034712 |
| 10 | 32602328 |
| 11 | 267535086 |
| 12 | 2223463866 |
| 13 | 18676869400 |
| 14 | 158310871740 |
| 15 | 1352392098120 |
| 16 | 11631593739990 |
| 17 | 100637721972216 |
| 18 | 875325840117960 |
| 19 | 7649219033276888 |
| 20 | 67126255864788120 |
| 21 | 591311470790795040 |
| 22 | 5226783343136641530 |
[2,6,30,182,1224,8778,65780,508950,4034712, 32602328,267535086,2223463866,18676869400, 158310871740,1352392098120,11631593739990, 100637721972216,875325840117960,7649219033276888, 67126255864788120,591311470790795040, 5226783343136641530] |