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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 8 |
| 5 | 18 |
| 6 | 90 |
| 7 | 301 |
| 8 | 1413 |
| 9 | 5628 |
| 10 | 26083 |
| 11 | 114133 |
| 12 | 536065 |
| 13 | 2475101 |
| 14 | 11844488 |
| 15 | 56598072 |
| 16 | 275910093 |
| 17 | 1350392157 |
| 18 | 6692423872 |
| 19 | 33348850521 |
| 20 | 167631991925 |
| 21 | 847255772901 |
| 22 | 4310527391729 |
| 23 | 22040709981279 |
| 24 | 113295384193957 |
| 25 | 584965125869980 |
| 26 | 3033583060169821 |
| 27 | 15793448306316644 |
| 28 | 82532818466952627 |
[1,0,1,1,8,18,90,301,1413,5628,26083,114133, 536065,2475101,11844488,56598072,275910093, 1350392157,6692423872,33348850521,167631991925, 847255772901,4310527391729,22040709981279, 113295384193957,584965125869980,3033583060169821, 15793448306316644,82532818466952627] |