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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 11 |
| 5 | 40 |
| 6 | 166 |
| 7 | 658 |
| 8 | 2647 |
| 9 | 10592 |
| 10 | 42446 |
| 11 | 169972 |
| 12 | 680670 |
| 13 | 2725320 |
| 14 | 10910992 |
| 15 | 43678882 |
| 16 | 174843151 |
| 17 | 699839680 |
| 18 | 2801078662 |
| 19 | 11210671612 |
| 20 | 44866276906 |
| 21 | 179552951440 |
| 22 | 718539964132 |
| 23 | 2875389341332 |
| 24 | 11506176209206 |
| 25 | 46042099714240 |
| 26 | 184234059839116 |
| 27 | 737184620655368 |
[0,0,1,2,11,40,166,658,2647,10592,42446,169972, 680670,2725320,10910992,43678882,174843151, 699839680,2801078662,11210671612,44866276906, 179552951440,718539964132,2875389341332, 11506176209206,46042099714240,184234059839116, 737184620655368] |