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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 48 |
| 5 | 186 |
| 6 | 754 |
| 7 | 3101 |
| 8 | 13081 |
| 9 | 55918 |
| 10 | 241842 |
| 11 | 1056729 |
| 12 | 4653512 |
| 13 | 20636905 |
| 14 | 92045421 |
| 15 | 412664764 |
| 16 | 1858189426 |
| 17 | 8400280703 |
| 18 | 38106109901 |
| 19 | 173399399510 |
| 20 | 791243931982 |
| 21 | 3619695024654 |
| 22 | 16597056340441 |
| 23 | 76261008077190 |
| 24 | 351083803055512 |
| 25 | 1619160434708842 |
| 26 | 7479651981112689 |
| 27 | 34604569511020325 |
[1,1,4,13,48,186,754,3101,13081,55918,241842, 1056729,4653512,20636905,92045421,412664764, 1858189426,8400280703,38106109901,173399399510, 791243931982,3619695024654,16597056340441, 76261008077190,351083803055512,1619160434708842, 7479651981112689,34604569511020325] |