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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 49 |
| 4 | 384 |
| 5 | 3025 |
| 6 | 23814 |
| 7 | 187489 |
| 8 | 1476096 |
| 9 | 11621281 |
| 10 | 91494150 |
| 11 | 720331921 |
| 12 | 5671161216 |
| 13 | 44648957809 |
| 14 | 351520501254 |
| 15 | 2767515052225 |
| 16 | 21788599916544 |
| 17 | 171541284280129 |
| 18 | 1350541674324486 |
| 19 | 10632792110315761 |
| 20 | 83711795208201600 |
[0,1,6,49,384,3025,23814,187489,1476096,11621281, 91494150,720331921,5671161216,44648957809, 351520501254,2767515052225,21788599916544, 171541284280129,1350541674324486, 10632792110315761,83711795208201600] |