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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 12 |
| 4 | 61 |
| 5 | 288 |
| 6 | 1488 |
| 7 | 7836 |
| 8 | 42593 |
| 9 | 236130 |
| 10 | 1333130 |
| 11 | 7636298 |
| 12 | 44294040 |
| 13 | 259682196 |
| 14 | 1536666930 |
| 15 | 9167492664 |
| 16 | 55086510571 |
| 17 | 333133752902 |
| 18 | 2026193778596 |
| 19 | 12387543671686 |
| 20 | 76088580071361 |
| 21 | 469354099705916 |
| 22 | 2906492292139022 |
[0,4,12,61,288,1488,7836,42593,236130,1333130, 7636298,44294040,259682196,1536666930,9167492664, 55086510571,333133752902,2026193778596, 12387543671686,76088580071361,469354099705916, 2906492292139022] |