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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 88 |
| 6 | 370 |
| 7 | 1613 |
| 8 | 7230 |
| 9 | 33117 |
| 10 | 154330 |
| 11 | 729369 |
| 12 | 3487470 |
| 13 | 16840346 |
| 14 | 82007012 |
| 15 | 402269702 |
| 16 | 1985867630 |
| 17 | 9858739759 |
| 18 | 49187798158 |
| 19 | 246506563980 |
| 20 | 1240337033398 |
| 21 | 6263601365616 |
| 22 | 31734939452116 |
| 23 | 161270637750264 |
| 24 | 821802841072422 |
| 25 | 4198348868249768 |
[1,1,2,6,22,88,370,1613,7230,33117,154330,729369, 3487470,16840346,82007012,402269702,1985867630, 9858739759,49187798158,246506563980,1240337033398, 6263601365616,31734939452116,161270637750264, 821802841072422,4198348868249768] |