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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 48 |
| 5 | 178 |
| 6 | 754 |
| 7 | 3038 |
| 8 | 13256 |
| 9 | 55906 |
| 10 | 248271 |
| 11 | 1076925 |
| 12 | 4840280 |
| 13 | 21389969 |
| 14 | 96984712 |
| 15 | 434253552 |
| 16 | 1982076992 |
| 17 | 8961513922 |
| 18 | 41116947235 |
| 19 | 187290133997 |
| 20 | 862948817693 |
| 21 | 3953887643326 |
| 22 | 18281451451847 |
| 23 | 84159204195508 |
| 24 | 390271429012935 |
| 25 | 1803618899480382 |
| 26 | 8385043953400396 |
| 27 | 38877111598742579 |
[1,1,4,12,48,178,754,3038,13256,55906,248271, 1076925,4840280,21389969,96984712,434253552, 1982076992,8961513922,41116947235,187290133997, 862948817693,3953887643326,18281451451847, 84159204195508,390271429012935,1803618899480382, 8385043953400396,38877111598742579] |