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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 33 |
| 3 | 162 |
| 4 | 756 |
| 5 | 3402 |
| 6 | 14931 |
| 7 | 64314 |
| 8 | 273051 |
| 9 | 1145988 |
| 10 | 4764744 |
| 11 | 19656756 |
| 12 | 80561061 |
| 13 | 328316814 |
| 14 | 1331513397 |
| 15 | 5377120038 |
| 16 | 21633427836 |
| 17 | 86747114430 |
| 18 | 346810621815 |
| 19 | 1382826606210 |
| 20 | 5500378861551 |
| 21 | 21830478128136 |
| 22 | 86469557676048 |
[1,6,33,162,756,3402,14931,64314,273051,1145988, 4764744,19656756,80561061,328316814,1331513397, 5377120038,21633427836,86747114430,346810621815, 1382826606210,5500378861551,21830478128136, 86469557676048] |