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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 7 |
| 5 | 38 |
| 6 | 192 |
| 7 | 946 |
| 8 | 4616 |
| 9 | 22440 |
| 10 | 108964 |
| 11 | 529133 |
| 12 | 2571079 |
| 13 | 12504038 |
| 14 | 60872038 |
| 15 | 296641049 |
| 16 | 1447054867 |
| 17 | 7065841496 |
| 18 | 34534088328 |
| 19 | 168933369259 |
| 20 | 827073303197 |
| 21 | 4052396628306 |
| 22 | 19870029768028 |
| 23 | 97495408609784 |
[0,0,0,1,7,38,192,946,4616,22440,108964,529133, 2571079,12504038,60872038,296641049,1447054867, 7065841496,34534088328,168933369259,827073303197, 4052396628306,19870029768028,97495408609784] |