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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 13 |
| 3 | 72 |
| 4 | 464 |
| 5 | 2853 |
| 6 | 17617 |
| 7 | 108785 |
| 8 | 671452 |
| 9 | 4144996 |
| 10 | 25586605 |
| 11 | 157944449 |
| 12 | 974979853 |
| 13 | 6018479996 |
| 14 | 37151644524 |
| 15 | 229334423389 |
| 16 | 1415664871777 |
| 17 | 8738797243193 |
| 18 | 53943965676260 |
| 19 | 332992213004236 |
| 20 | 2055536935944305 |
[1,13,72,464,2853,17617,108785,671452,4144996, 25586605,157944449,974979853,6018479996, 37151644524,229334423389,1415664871777, 8738797243193,53943965676260,332992213004236, 2055536935944305] |