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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 13 |
| 2 | 120 |
| 3 | 847 |
| 4 | 5460 |
| 5 | 33883 |
| 6 | 206640 |
| 7 | 1249807 |
| 8 | 7528620 |
| 9 | 45260803 |
| 10 | 271831560 |
| 11 | 1631788567 |
| 12 | 9793126980 |
| 13 | 58765944523 |
| 14 | 352617206880 |
| 15 | 2115767844127 |
| 16 | 12694800840540 |
| 17 | 76169386305043 |
| 18 | 457018061484600 |
| 19 | 2742113599608487 |
| 20 | 16452697289229300 |
| 21 | 98716230809062363 |
[0,13,120,847,5460,33883,206640,1249807,7528620, 45260803,271831560,1631788567,9793126980, 58765944523,352617206880,2115767844127, 12694800840540,76169386305043,457018061484600, 2742113599608487,16452697289229300, 98716230809062363] |