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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 13 |
| 3 | 63 |
| 4 | 319 |
| 5 | 1647 |
| 6 | 8583 |
| 7 | 44941 |
| 8 | 235913 |
| 9 | 1240173 |
| 10 | 6524919 |
| 11 | 34346785 |
| 12 | 180855499 |
| 13 | 952494047 |
| 14 | 5017037457 |
| 15 | 26428222177 |
| 16 | 139223327493 |
| 17 | 733452042061 |
| 18 | 3864043260671 |
| 19 | 20357263645411 |
| 20 | 107251092223601 |
| 21 | 565050705077767 |
[1,3,13,63,319,1647,8583,44941,235913,1240173, 6524919,34346785,180855499,952494047,5017037457, 26428222177,139223327493,733452042061, 3864043260671,20357263645411,107251092223601, 565050705077767] |