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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 82 |
| 5 | 370 |
| 6 | 1648 |
| 7 | 7252 |
| 8 | 31582 |
| 9 | 136338 |
| 10 | 584248 |
| 11 | 2488156 |
| 12 | 10540484 |
| 13 | 44450068 |
| 14 | 186715072 |
| 15 | 781628008 |
| 16 | 3262239862 |
| 17 | 13579324498 |
| 18 | 56391614632 |
| 19 | 233686316428 |
| 20 | 966556003132 |
| 21 | 3990942300508 |
| 22 | 16453094542432 |
| 23 | 67733512006168 |
[1,4,18,82,370,1648,7252,31582,136338,584248, 2488156,10540484,44450068,186715072,781628008, 3262239862,13579324498,56391614632,233686316428, 966556003132,3990942300508,16453094542432, 67733512006168] |