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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 9 |
| 7 | 76 |
| 8 | 542 |
| 9 | 3523 |
| 10 | 21393 |
| 11 | 123680 |
| 12 | 690550 |
| 13 | 3756151 |
| 14 | 20042589 |
| 15 | 105394296 |
| 16 | 548123982 |
| 17 | 2826435403 |
| 18 | 14479204833 |
| 19 | 73794961960 |
| 20 | 374603884910 |
| 21 | 1895632969351 |
| 22 | 9568915372269 |
| 23 | 48208452866816 |
[0,0,0,0,1,9,76,542,3523,21393,123680,690550, 3756151,20042589,105394296,548123982,2826435403, 14479204833,73794961960,374603884910, 1895632969351,9568915372269,48208452866816] |