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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 11 |
| 6 | 44 |
| 7 | 169 |
| 8 | 588 |
| 9 | 1948 |
| 10 | 6560 |
| 11 | 23133 |
| 12 | 84565 |
| 13 | 317755 |
| 14 | 1198336 |
| 15 | 4509419 |
| 16 | 16909184 |
| 17 | 63409935 |
| 18 | 238609052 |
| 19 | 902444517 |
| 20 | 3429249843 |
| 21 | 13076666409 |
| 22 | 49977802752 |
| 23 | 191312873561 |
| 24 | 733365845820 |
| 25 | 2815437297416 |
| 26 | 10825960652800 |
| 27 | 41694907460224 |
| 28 | 160823207301705 |
[1,0,1,1,11,44,169,588,1948,6560,23133,84565, 317755,1198336,4509419,16909184,63409935, 238609052,902444517,3429249843,13076666409, 49977802752,191312873561,733365845820, 2815437297416,10825960652800,41694907460224, 160823207301705] |