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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 89 |
| 5 | 577 |
| 6 | 3954 |
| 7 | 28159 |
| 8 | 206344 |
| 9 | 1545851 |
| 10 | 11787445 |
| 11 | 91191974 |
| 12 | 714062041 |
| 13 | 5648777429 |
| 14 | 45079529911 |
| 15 | 362495811596 |
| 16 | 2934348587956 |
| 17 | 23892641086459 |
| 18 | 195557929860835 |
| 19 | 1608071398391111 |
| 20 | 13278516834574055 |
| 21 | 110060894070407408 |
| 22 | 915386559028780435 |
[0,1,3,15,89,577,3954,28159,206344,1545851, 11787445,91191974,714062041,5648777429, 45079529911,362495811596,2934348587956, 23892641086459,195557929860835,1608071398391111, 13278516834574055,110060894070407408, 915386559028780435] |