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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 71 |
| 6 | 322 |
| 7 | 1665 |
| 8 | 9789 |
| 9 | 64327 |
| 10 | 468914 |
| 11 | 3748920 |
| 12 | 32699022 |
| 13 | 308710917 |
| 14 | 3138821688 |
| 15 | 34186918427 |
| 16 | 397173376849 |
| 17 | 4902547569617 |
| 18 | 64073734206528 |
| 19 | 883940288032392 |
| 20 | 12836250526983672 |
| 21 | 195724485831901029 |
| 22 | 3126468139092090818 |
| 23 | 52211816154041174670 |
| 24 | 909843384081141844312 |
[1,1,2,6,18,71,322,1665,9789,64327,468914,3748920, 32699022,308710917,3138821688,34186918427, 397173376849,4902547569617,64073734206528, 883940288032392,12836250526983672, 195724485831901029,3126468139092090818, 52211816154041174670,909843384081141844312] |