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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 10 |
| 6 | 22 |
| 7 | 63 |
| 8 | 168 |
| 9 | 398 |
| 10 | 864 |
| 11 | 1998 |
| 12 | 4814 |
| 13 | 11515 |
| 14 | 27219 |
| 15 | 64834 |
| 16 | 155776 |
| 17 | 370324 |
| 18 | 875660 |
| 19 | 2075443 |
| 20 | 4937760 |
| 21 | 11743610 |
| 22 | 27890804 |
| 23 | 66275841 |
| 24 | 157582669 |
| 25 | 374562749 |
| 26 | 889810081 |
| 27 | 2114058291 |
| 28 | 5024124329 |
| 29 | 11940009567 |
| 30 | 28372771969 |
| 31 | 67421703499 |
[1,1,1,4,10,22,63,168,398,864,1998,4814,11515, 27219,64834,155776,370324,875660,2075443,4937760, 11743610,27890804,66275841,157582669,374562749, 889810081,2114058291,5024124329,11940009567, 28372771969,67421703499] |