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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 20 |
| 6 | 51 |
| 7 | 125 |
| 8 | 329 |
| 9 | 862 |
| 10 | 2311 |
| 11 | 6217 |
| 12 | 16949 |
| 13 | 46350 |
| 14 | 127714 |
| 15 | 353272 |
| 16 | 981753 |
| 17 | 2737539 |
| 18 | 7659789 |
| 19 | 21492286 |
| 20 | 60466130 |
| 21 | 170510030 |
| 22 | 481867683 |
| 23 | 1364424829 |
| 24 | 3870373826 |
| 25 | 10996890237 |
| 26 | 31293083540 |
| 27 | 89173833915 |
| 28 | 254445242754 |
| 29 | 726907585652 |
| 30 | 2079012341822 |
[1,2,4,9,20,51,125,329,862,2311,6217,16949,46350, 127714,353272,981753,2737539,7659789,21492286, 60466130,170510030,481867683,1364424829, 3870373826,10996890237,31293083540,89173833915, 254445242754,726907585652,2079012341822] |