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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 420 |
| 4 | 15225 |
| 5 | 185031 |
| 6 | 1438906 |
| 7 | 8689306 |
| 8 | 44352346 |
| 9 | 200070606 |
| 10 | 818907792 |
| 11 | 3093635652 |
| 12 | 10914809127 |
| 13 | 36278256537 |
| 14 | 114357327402 |
| 15 | 343708626298 |
| 16 | 989318816383 |
| 17 | 2737219679833 |
| 18 | 7302776865288 |
| 19 | 18839417766108 |
| 20 | 47108352127209 |
| 21 | 114421884019959 |
[0,0,420,15225,185031,1438906,8689306,44352346, 200070606,818907792,3093635652,10914809127, 36278256537,114357327402,343708626298, 989318816383,2737219679833,7302776865288, 18839417766108,47108352127209,114421884019959] |