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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 51 |
| 5 | 205 |
| 6 | 863 |
| 7 | 3735 |
| 8 | 16485 |
| 9 | 74044 |
| 10 | 336717 |
| 11 | 1547700 |
| 12 | 7175187 |
| 13 | 33505829 |
| 14 | 157423145 |
| 15 | 743479522 |
| 16 | 3527237161 |
| 17 | 16799557266 |
| 18 | 80288255265 |
| 19 | 384876372364 |
| 20 | 1849943233443 |
| 21 | 8913270844596 |
| 22 | 43037808241896 |
| 23 | 208211887956508 |
| 24 | 1009073596684092 |
| 25 | 4898153235733664 |
| 26 | 23810753170107055 |
| 27 | 115902118316694161 |
[1,1,4,13,51,205,863,3735,16485,74044,336717, 1547700,7175187,33505829,157423145,743479522, 3527237161,16799557266,80288255265,384876372364, 1849943233443,8913270844596,43037808241896, 208211887956508,1009073596684092,4898153235733664, 23810753170107055,115902118316694161] |