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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 9 |
| 4 | 26 |
| 5 | 74 |
| 6 | 208 |
| 7 | 586 |
| 8 | 1647 |
| 9 | 4646 |
| 10 | 13135 |
| 11 | 37247 |
| 12 | 105896 |
| 13 | 301880 |
| 14 | 862498 |
| 15 | 2469480 |
| 16 | 7083690 |
| 17 | 20353886 |
| 18 | 58571805 |
| 19 | 168780848 |
| 20 | 486958481 |
| 21 | 1406524978 |
| 22 | 4066735979 |
| 23 | 11769294050 |
| 24 | 34090034328 |
| 25 | 98820719105 |
| 26 | 286672555274 |
[0,1,3,9,26,74,208,586,1647,4646,13135,37247, 105896,301880,862498,2469480,7083690,20353886, 58571805,168780848,486958481,1406524978, 4066735979,11769294050,34090034328,98820719105, 286672555274] |