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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 52 |
| 6 | 164 |
| 7 | 476 |
| 8 | 1428 |
| 9 | 4308 |
| 10 | 12816 |
| 11 | 38324 |
| 12 | 114924 |
| 13 | 343696 |
| 14 | 1028096 |
| 15 | 3077672 |
| 16 | 9209704 |
| 17 | 27556452 |
| 18 | 82465380 |
| 19 | 246779888 |
| 20 | 738461796 |
| 21 | 2209820148 |
| 22 | 6612853424 |
| 23 | 19788642456 |
| 24 | 59216642832 |
| 25 | 177203814880 |
| 26 | 530275470412 |
| 27 | 1586827690308 |
[1,2,6,16,52,164,476,1428,4308,12816,38324,114924, 343696,1028096,3077672,9209704,27556452,82465380, 246779888,738461796,2209820148,6612853424, 19788642456,59216642832,177203814880,530275470412, 1586827690308] |